Checkpoint: Initial stable CheckFlow base before i18n and demo mode

.env.example

@@ -0,0 +1,11 @@
+# Database password (change in production!)
+POSTGRES_PASSWORD=changeme
+
+# App URL (set to your domain or server IP)
+NEXTAUTH_URL=http://localhost:3000
+
+# Auth secret — generate with: openssl rand -base64 32
+NEXTAUTH_SECRET=change-this-to-a-random-string
+
+# Port to expose (default 3000)
+PORT=3000

.gitignore

@@ -1,41 +1,18 @@
-# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
+# deps
+node_modules/
+.pnp
+.pnp.js
 
-# dependencies
+# next
-/node_modules
+.next/
-/.pnp
+out/
-.pnp.*
-.yarn/*
-!.yarn/patches
-!.yarn/plugins
-!.yarn/releases
-!.yarn/versions
 
-# testing
+# env
-/coverage
+.env
-
+.env.local
-# next.js
+.env.production
-/.next/
-/out/
-
-# production
-/build
 
 # misc
 .DS_Store
 *.pem
-
+npm-debug.log*
-# debug
-npm-debug.log*
-yarn-debug.log*
-yarn-error.log*
-.pnpm-debug.log*
-
-# env files (can opt-in for committing if needed)
-.env*
-
-# vercel
-.vercel
-
-# typescript
-*.tsbuildinfo
-next-env.d.ts

Dockerfile

@@ -0,0 +1,29 @@
+FROM node:20-alpine AS base
+WORKDIR /app
+
+FROM base AS deps
+COPY package.json package-lock.json ./
+RUN npm ci --legacy-peer-deps
+
+FROM base AS builder
+COPY --from=deps /app/node_modules ./node_modules
+COPY . .
+RUN npx prisma generate
+RUN npm run build
+
+FROM base AS runner
+ENV NODE_ENV=production
+RUN addgroup --system --gid 1001 nodejs && adduser --system --uid 1001 nextjs
+COPY --from=builder /app/.next/standalone ./
+COPY --from=builder /app/.next/static ./.next/static
+COPY --from=builder /app/public ./public
+COPY --from=builder /app/prisma ./prisma
+COPY --from=builder /app/node_modules/.prisma ./node_modules/.prisma
+COPY --from=builder /app/node_modules/@prisma ./node_modules/@prisma
+
+USER nextjs
+EXPOSE 3000
+ENV PORT=3000
+ENV HOSTNAME="0.0.0.0"
+
+CMD ["node", "server.js"]

README.md

@@ -1,36 +1,117 @@
-This is a [Next.js](https://nextjs.org) project bootstrapped with [`create-next-app`](https://nextjs.org/docs/app/api-reference/cli/create-next-app).
+# CheckFlow
 
-## Getting Started
+> 셀프호스팅 TickTick-like Todo 앱 — 계층형 체크리스트 + 메모장 + CardDAV + PWA
 
-First, run the development server:
+![CheckFlow](public/icons/icon.svg)
+
+## 주요 기능
+
+- ✅ **계층형 체크리스트** — 메인 태스크 + 하위 태스크
+- 📝 **태스크 메모장** — 넓은 노트 영역 (Markdown 지원)
+- 👥 **멀티유저** — 각 사용자 데이터 완전 격리
+- 📱 **PWA** — Android 홈 화면 추가, 오프라인 지원
+- 📲 **CardDAV** — DAVx⁵ 앱으로 Galaxy 동기화
+- 📥 **TickTick Import** — CSV/ICS 내보내기 파일 import
+- 🌙 **다크모드** — 시스템/수동 전환
+- 🐳 **Docker** — 원클릭 배포
+
+## 빠른 시작
+
+### 1. 환경 변수 설정
 
 ```bash
-npm run dev
+cp .env.example .env
-# or
+# .env 파일에서 NEXTAUTH_SECRET 및 POSTGRES_PASSWORD 변경
-yarn dev
-# or
-pnpm dev
-# or
-bun dev
 ```
 
-Open [http://localhost:3000](http://localhost:3000) with your browser to see the result.
+### 2. Docker로 실행
 
-You can start editing the page by modifying `app/page.tsx`. The page auto-updates as you edit the file.
+```bash
+docker compose up -d
+```
 
-This project uses [`next/font`](https://nextjs.org/docs/app/building-your-application/optimizing/fonts) to automatically optimize and load [Geist](https://vercel.com/font), a new font family for Vercel.
+앱이 시작되면:
+```bash
+# DB 마이그레이션 (최초 1회)
+docker compose exec app npx prisma migrate deploy
+```
 
-## Learn More
+`http://localhost:3000` 접속 후 계정 생성.
 
-To learn more about Next.js, take a look at the following resources:
+---
 
-- [Next.js Documentation](https://nextjs.org/docs) - learn about Next.js features and API.
+## 개발 환경 실행
-- [Learn Next.js](https://nextjs.org/learn) - an interactive Next.js tutorial.
 
-You can check out [the Next.js GitHub repository](https://github.com/vercel/next.js) - your feedback and contributions are welcome!
+### 요구사항
+- Node.js 20+
+- PostgreSQL (또는 Docker)
 
-## Deploy on Vercel
+```bash
+# 의존성 설치
+npm install
 
-The easiest way to deploy your Next.js app is to use the [Vercel Platform](https://vercel.com/new?utm_medium=default-template&filter=next.js&utm_source=create-next-app&utm_campaign=create-next-app-readme) from the creators of Next.js.
+# DB 설정
+cp .env.example .env.local
+# .env.local의 DATABASE_URL을 DB에 맞게 수정
 
-Check out our [Next.js deployment documentation](https://nextjs.org/docs/app/building-your-application/deploying) for more details.
+# DB 마이그레이션
+npx prisma migrate dev
+
+# 개발 서버 시작
+npm run dev
+```
+
+→ `http://localhost:3000`
+
+---
+
+## DAVx⁵로 Galaxy 연동
+
+1. Play Store에서 **[DAVx⁵](https://play.google.com/store/apps/details?id=at.bitfire.davdroid)** 설치 (무료)
+2. DAVx⁵ 앱 → **+** → Login with URL and user name
+   - **URL**: `http://your-server:3000/api/dav`
+   - **Username**: CheckFlow 이메일
+   - **Password**: CheckFlow 비밀번호
+3. Task 목록 동기화 → Samsung Reminder 또는 Tasks 앱에서 확인
+
+---
+
+## TickTick에서 가져오기
+
+1. TickTick 앱 → Settings → Export
+2. **Export as CSV** 또는 **Export as iCalendar** 선택
+3. CheckFlow → 사이드바 → **Import Tasks**
+4. 파일 선택 후 대상 목록 지정 → Import
+
+---
+
+## NPM (Nginx Proxy Manager) 연동
+
+Docker compose가 기본으로 `3000` 포트에서 실행됩니다.
+NPM에서 Proxy Host 추가:
+- **Destination**: `http://checkflow-app:3000`
+- SSL 인증서 설정
+
+---
+
+## 환경 변수
+
+| 변수 | 설명 | 기본값 |
+|------|------|--------|
+| `DATABASE_URL` | PostgreSQL 연결 문자열 | — |
+| `NEXTAUTH_URL` | 외부 접근 URL | `http://localhost:3000` |
+| `NEXTAUTH_SECRET` | JWT 시크릿 (32자 이상 랜덤) | — |
+| `POSTGRES_PASSWORD` | DB 비밀번호 | `changeme` |
+| `PORT` | 노출 포트 | `3000` |
+
+---
+
+## 기술 스택
+
+- **Frontend**: Next.js 16 (App Router) + TypeScript + Vanilla CSS
+- **Backend**: Next.js API Routes
+- **DB**: PostgreSQL + Prisma ORM
+- **Auth**: NextAuth.js (JWT)
+- **PWA**: Service Worker + Web App Manifest
+- **CardDAV**: 커스텀 iCalendar VTODO 구현
+- **Container**: Docker + docker-compose

docker-compose.yml

@@ -0,0 +1,49 @@
+version: "3.9"
+
+services:
+  postgres:
+    image: postgres:16-alpine
+    container_name: checkflow-db
+    restart: unless-stopped
+    environment:
+      POSTGRES_DB: checkflow
+      POSTGRES_USER: checkflow
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-changeme}
+    volumes:
+      - postgres_data:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U checkflow"]
+      interval: 10s
+      timeout: 5s
+      retries: 5
+
+  migrate:
+    build: .
+    container_name: checkflow-migrate
+    depends_on:
+      postgres:
+        condition: service_healthy
+    environment:
+      DATABASE_URL: postgresql://checkflow:${POSTGRES_PASSWORD:-changeme}@postgres:5432/checkflow
+    command: npx prisma migrate deploy
+    restart: "no"
+
+  app:
+    build: .
+    container_name: checkflow-app
+    restart: unless-stopped
+    depends_on:
+      migrate:
+        condition: service_completed_successfully
+    ports:
+      - "${PORT:-3000}:3000"
+    environment:
+      DATABASE_URL: postgresql://checkflow:${POSTGRES_PASSWORD:-changeme}@postgres:5432/checkflow
+      NEXTAUTH_URL: ${NEXTAUTH_URL:-http://localhost:3000}
+      NEXTAUTH_SECRET: ${NEXTAUTH_SECRET:-change-this-secret-in-production}
+      NODE_ENV: production
+    volumes:
+      - ./prisma:/app/prisma
+
+volumes:
+  postgres_data:

next-env.d.ts

@@ -0,0 +1,7 @@
+/// <reference types="next" />
+/// <reference types="next/image-types/global" />
+import "./.next/types/routes.d.ts";
+import "./.next/types/root-params.d.ts";
+
+// NOTE: This file should not be edited
+// see https://nextjs.org/docs/app/api-reference/config/typescript for more information.

next.config.ts

@@ -1,7 +1,16 @@
 import type { NextConfig } from "next";
 
 const nextConfig: NextConfig = {
-  /* config options here */
+  output: "standalone",
+  // PWA service worker (manual - no next-pwa needed)
+  async headers() {
+    return [
+      {
+        source: "/manifest.json",
+        headers: [{ key: "Content-Type", value: "application/manifest+json" }],
+      },
+    ];
+  },
 };
 
-export default nextConfig;
+export default nextConfig;

package-lock.json

@@ -8,15 +8,26 @@
       "name": "checkflow",
       "version": "0.1.0",
       "dependencies": {
+        "@dnd-kit/core": "^6.3.1",
+        "@dnd-kit/sortable": "^10.0.0",
+        "@dnd-kit/utilities": "^3.2.2",
+        "@prisma/client": "^6.19.3",
+        "bcryptjs": "^3.0.3",
+        "csv-parse": "^7.0.2",
         "next": "16.3.1",
+        "next-auth": "^4.24.15",
+        "prisma": "^6.19.3",
         "react": "19.2.8",
-        "react-dom": "19.2.8"
+        "react-dom": "19.2.8",
+        "uuid": "^14.0.2"
       },
       "devDependencies": {
         "@tailwindcss/postcss": "^4",
+        "@types/bcryptjs": "^3.0.0",
         "@types/node": "^20",
         "@types/react": "^19",
         "@types/react-dom": "^19",
+        "@types/uuid": "^11.0.0",
         "eslint": "^9",
         "eslint-config-next": "16.3.1",
         "tailwindcss": "^4",
@@ -214,6 +225,14 @@
         "node": ">=6.0.0"
       }
     },
+    "node_modules/@babel/runtime": {
+      "version": "7.29.7",
+      "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.29.7.tgz",
+      "integrity": "sha512-Nq8OhGWiZIZGV6hLHoyAKLLcJihP/xFeBMGJoUrxTX2psI8dCifzLhZISFb+VWS3wFMRDmCGw5R+dOySCqPLhw==",
+      "engines": {
+        "node": ">=6.9.0"
+      }
+    },
     "node_modules/@babel/template": {
       "version": "7.29.7",
       "resolved": "https://registry.npmjs.org/@babel/template/-/template-7.29.7.tgz",
@@ -259,6 +278,55 @@
         "node": ">=6.9.0"
       }
     },
+    "node_modules/@dnd-kit/accessibility": {
+      "version": "3.1.1",
+      "resolved": "https://registry.npmjs.org/@dnd-kit/accessibility/-/accessibility-3.1.1.tgz",
+      "integrity": "sha512-2P+YgaXF+gRsIihwwY1gCsQSYnu9Zyj2py8kY5fFvUM1qm2WA2u639R6YNVfU4GWr+ZM5mqEsfHZZLoRONbemw==",
+      "dependencies": {
+        "tslib": "^2.0.0"
+      },
+      "peerDependencies": {
+        "react": ">=16.8.0"
+      }
+    },
+    "node_modules/@dnd-kit/core": {
+      "version": "6.3.1",
+      "resolved": "https://registry.npmjs.org/@dnd-kit/core/-/core-6.3.1.tgz",
+      "integrity": "sha512-xkGBRQQab4RLwgXxoqETICr6S5JlogafbhNsidmrkVv2YRs5MLwpjoF2qpiGjQt8S9AoxtIV603s0GIUpY5eYQ==",
+      "dependencies": {
+        "@dnd-kit/accessibility": "^3.1.1",
+        "@dnd-kit/utilities": "^3.2.2",
+        "tslib": "^2.0.0"
+      },
+      "peerDependencies": {
+        "react": ">=16.8.0",
+        "react-dom": ">=16.8.0"
+      }
+    },
+    "node_modules/@dnd-kit/sortable": {
+      "version": "10.0.0",
+      "resolved": "https://registry.npmjs.org/@dnd-kit/sortable/-/sortable-10.0.0.tgz",
+      "integrity": "sha512-+xqhmIIzvAYMGfBYYnbKuNicfSsk4RksY2XdmJhT+HAC01nix6fHCztU68jooFiMUB01Ky3F0FyOvhG/BZrWkg==",
+      "dependencies": {
+        "@dnd-kit/utilities": "^3.2.2",
+        "tslib": "^2.0.0"
+      },
+      "peerDependencies": {
+        "@dnd-kit/core": "^6.3.0",
+        "react": ">=16.8.0"
+      }
+    },
+    "node_modules/@dnd-kit/utilities": {
+      "version": "3.2.2",
+      "resolved": "https://registry.npmjs.org/@dnd-kit/utilities/-/utilities-3.2.2.tgz",
+      "integrity": "sha512-+MKAJEOfaBe5SmV6t34p80MMKhjvUz0vRrvVJbPT0WElzaOJ/1xs+D+KDv+tD/NE5ujfrChEcshd4fLn0wpiqg==",
+      "dependencies": {
+        "tslib": "^2.0.0"
+      },
+      "peerDependencies": {
+        "react": ">=16.8.0"
+      }
+    },
     "node_modules/@emnapi/core": {
       "version": "1.10.0",
       "resolved": "https://registry.npmjs.org/@emnapi/core/-/core-1.10.0.tgz",
@@ -1233,12 +1301,97 @@
         "node": ">=12.4.0"
       }
     },
+    "node_modules/@panva/hkdf": {
+      "version": "1.2.1",
+      "resolved": "https://registry.npmjs.org/@panva/hkdf/-/hkdf-1.2.1.tgz",
+      "integrity": "sha512-6oclG6Y3PiDFcoyk8srjLfVKyMfVCKJ27JwNPViuXziFpmdz+MZnZN/aKY0JGXgYuO/VghU0jcOAZgWXZ1Dmrw==",
+      "funding": {
+        "url": "https://github.com/sponsors/panva"
+      }
+    },
+    "node_modules/@prisma/client": {
+      "version": "6.19.3",
+      "resolved": "https://registry.npmjs.org/@prisma/client/-/client-6.19.3.tgz",
+      "integrity": "sha512-mKq3jQFhjvko5LTJFHGilsuQs+W+T3Gm451NzuTDGQxwCzwXHYnIu2zGkRoW+Exq3Rob7yp2MfzSrdIiZVhrBg==",
+      "hasInstallScript": true,
+      "engines": {
+        "node": ">=18.18"
+      },
+      "peerDependencies": {
+        "prisma": "*",
+        "typescript": ">=5.1.0"
+      },
+      "peerDependenciesMeta": {
+        "prisma": {
+          "optional": true
+        },
+        "typescript": {
+          "optional": true
+        }
+      }
+    },
+    "node_modules/@prisma/config": {
+      "version": "6.19.3",
+      "resolved": "https://registry.npmjs.org/@prisma/config/-/config-6.19.3.tgz",
+      "integrity": "sha512-CBPT44BjlQxEt8kiMEauji2WHTDoVBOKl7UlewXmUgBPnr/oPRZC3psci5chJnYmH0ivEIog2OU9PGWoki3DLQ==",
+      "dependencies": {
+        "c12": "3.1.0",
+        "deepmerge-ts": "7.1.5",
+        "effect": "3.21.0",
+        "empathic": "2.0.0"
+      }
+    },
+    "node_modules/@prisma/debug": {
+      "version": "6.19.3",
+      "resolved": "https://registry.npmjs.org/@prisma/debug/-/debug-6.19.3.tgz",
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+    },
+    "node_modules/@prisma/engines": {
+      "version": "6.19.3",
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+        "@prisma/fetch-engine": "6.19.3",
+        "@prisma/get-platform": "6.19.3"
+      }
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+    },
+    "node_modules/@prisma/fetch-engine": {
+      "version": "6.19.3",
+      "resolved": "https://registry.npmjs.org/@prisma/fetch-engine/-/fetch-engine-6.19.3.tgz",
+      "integrity": "sha512-tKtl/qco9Nt7LU5iKhpultD8O4vMCZcU2CHjNTnRrL1QvSUr5W/GcyFPjNL87GtRrwBc7ubXXD9xy4EvLvt8JA==",
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+        "@prisma/debug": "6.19.3",
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+        "@prisma/get-platform": "6.19.3"
+      }
+    },
+    "node_modules/@prisma/get-platform": {
+      "version": "6.19.3",
+      "resolved": "https://registry.npmjs.org/@prisma/get-platform/-/get-platform-6.19.3.tgz",
+      "integrity": "sha512-xFj1VcJ1N3MKooOQAGO0W5tsd0W2QzIvW7DD7c/8H14Zmp4jseeWAITm+w2LLoLrlhoHdPPh0NMZ8mfL6puoHA==",
+      "dependencies": {
+        "@prisma/debug": "6.19.3"
+      }
+    },
     "node_modules/@rtsao/scc": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/@rtsao/scc/-/scc-1.1.0.tgz",
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       "dev": true
     },
+    "node_modules/@standard-schema/spec": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/@standard-schema/spec/-/spec-1.1.0.tgz",
+      "integrity": "sha512-l2aFy5jALhniG5HgqrD6jXLi/rUWrKvqN/qJx6yoJsgKhblVd+iqqU4RCXavm/jPityDo5TCvKMnpjKnOriy0w=="
+    },
     "node_modules/@swc/helpers": {
       "version": "0.5.23",
       "resolved": "https://registry.npmjs.org/@swc/helpers/-/helpers-0.5.23.tgz",
@@ -1513,6 +1666,16 @@
         "tslib": "^2.4.0"
       }
     },
+    "node_modules/@types/bcryptjs": {
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/@types/bcryptjs/-/bcryptjs-3.0.0.tgz",
+      "integrity": "sha512-WRZOuCuaz8UcZZE4R5HXTco2goQSI2XxjGY3hbM/xDvwmqFWd4ivooImsMx65OKM6CtNKbnZ5YL+YwAwK7c1dg==",
+      "deprecated": "This is a stub types definition. bcryptjs provides its own type definitions, so you do not need this installed.",
+      "dev": true,
+      "dependencies": {
+        "bcryptjs": "*"
+      }
+    },
     "node_modules/@types/estree": {
       "version": "1.0.9",
       "resolved": "https://registry.npmjs.org/@types/estree/-/estree-1.0.9.tgz",
@@ -1558,6 +1721,16 @@
         "@types/react": "^19.2.0"
       }
     },
+    "node_modules/@types/uuid": {
+      "version": "11.0.0",
+      "resolved": "https://registry.npmjs.org/@types/uuid/-/uuid-11.0.0.tgz",
+      "integrity": "sha512-HVyk8nj2m+jcFRNazzqyVKiZezyhDKrGUA3jlEcg/nZ6Ms+qHwocba1Y/AaVaznJTAM9xpdFSh+ptbNrhOGvZA==",
+      "deprecated": "This is a stub types definition. uuid provides its own type definitions, so you do not need this installed.",
+      "dev": true,
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+      "dependencies": {
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+      },
+      "engines": {
+        "node": ">=10"
+      }
+    },
+    "node_modules/openid-client/node_modules/yallist": {
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/yallist/-/yallist-4.0.0.tgz",
+      "integrity": "sha512-3wdGidZyq5PB084XLES5TpOSRA3wjXAlIWMhum2kRcv/41Sn2emQ0dycQW4uZXLejwKvg6EsvbdlVL+FYEct7A=="
+    },
     "node_modules/optionator": {
       "version": "0.9.4",
       "resolved": "https://registry.npmjs.org/optionator/-/optionator-0.9.4.tgz",
@@ -5140,6 +5616,16 @@
       "integrity": "sha512-LDJzPVEEEPR+y48z93A0Ed0yXb8pAByGWo/k5YYdYgpY2/2EsOsksJrq7lOHxryrVOn1ejG6oAp8ahvOIQD8sw==",
       "dev": true
     },
+    "node_modules/pathe": {
+      "version": "2.0.3",
+      "resolved": "https://registry.npmjs.org/pathe/-/pathe-2.0.3.tgz",
+      "integrity": "sha512-WUjGcAqP1gQacoQe+OBJsFA7Ld4DyXuUIjZ5cc75cLHvJ7dtNsTugphxIADwspS+AraAUePCKrSVtPLFj/F88w=="
+    },
+    "node_modules/perfect-debounce": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/perfect-debounce/-/perfect-debounce-1.0.0.tgz",
+      "integrity": "sha512-xCy9V055GLEqoFaHoC1SoLIaLmWctgCUaBaWxDZ7/Zx4CTyX7cJQLJOok/orfjZAh9kEYpjJa4d0KcJmCbctZA=="
+    },
     "node_modules/picocolors": {
       "version": "1.1.1",
       "resolved": "https://registry.npmjs.org/picocolors/-/picocolors-1.1.1.tgz",
@@ -5157,6 +5643,16 @@
         "url": "https://github.com/sponsors/jonschlinkert"
       }
     },
+    "node_modules/pkg-types": {
+      "version": "2.3.1",
+      "resolved": "https://registry.npmjs.org/pkg-types/-/pkg-types-2.3.1.tgz",
+      "integrity": "sha512-y+ichcgc2LrADuhLNAx8DFjVfgz91pRxfZdI3UDhxHvcVEZsenLO+7XaU5vOp0u/7V/wZ+plyuQxtrDlZJ+yeg==",
+      "dependencies": {
+        "confbox": "^0.2.4",
+        "exsolve": "^1.0.8",
+        "pathe": "^2.0.3"
+      }
+    },
     "node_modules/possible-typed-array-names": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/possible-typed-array-names/-/possible-typed-array-names-1.1.0.tgz",
@@ -5194,6 +5690,34 @@
         "node": "^10 || ^12 || >=14"
       }
     },
+    "node_modules/preact": {
+      "version": "10.29.8",
+      "resolved": "https://registry.npmjs.org/preact/-/preact-10.29.8.tgz",
+      "integrity": "sha512-ej2aVZ+vZ8WO7tvlQWRM9N63A0KzF9q4mWJfDUHgYaIofWY9hu74QdnQrjoPMmZi2/nZ5gN0bJCQF49xQqx09Q==",
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/preact"
+      },
+      "peerDependencies": {
+        "preact-render-to-string": ">=5"
+      },
+      "peerDependenciesMeta": {
+        "preact-render-to-string": {
+          "optional": true
+        }
+      }
+    },
+    "node_modules/preact-render-to-string": {
+      "version": "5.2.6",
+      "resolved": "https://registry.npmjs.org/preact-render-to-string/-/preact-render-to-string-5.2.6.tgz",
+      "integrity": "sha512-JyhErpYOvBV1hEPwIxc/fHWXPfnEGdRKxc8gFdAZ7XV4tlzyzG847XAyEZqoDnynP88akM4eaHcSOzNcLWFguw==",
+      "dependencies": {
+        "pretty-format": "^3.8.0"
+      },
+      "peerDependencies": {
+        "preact": ">=10"
+      }
+    },
     "node_modules/prelude-ls": {
       "version": "1.2.1",
       "resolved": "https://registry.npmjs.org/prelude-ls/-/prelude-ls-1.2.1.tgz",
@@ -5203,6 +5727,35 @@
         "node": ">= 0.8.0"
       }
     },
+    "node_modules/pretty-format": {
+      "version": "3.8.0",
+      "resolved": "https://registry.npmjs.org/pretty-format/-/pretty-format-3.8.0.tgz",
+      "integrity": "sha512-WuxUnVtlWL1OfZFQFuqvnvs6MiAGk9UNsBostyBOB0Is9wb5uRESevA6rnl/rkksXaGX3GzZhPup5d6Vp1nFew=="
+    },
+    "node_modules/prisma": {
+      "version": "6.19.3",
+      "resolved": "https://registry.npmjs.org/prisma/-/prisma-6.19.3.tgz",
+      "integrity": "sha512-++ZJ0ijLrDJF6hNB4t4uxg2br3fC4H9Yc9tcbjr2fcNFP3rh/SBNrAgjhsqBU4Ght8JPrVofG/ZkXfnSfnYsFg==",
+      "hasInstallScript": true,
+      "dependencies": {
+        "@prisma/config": "6.19.3",
+        "@prisma/engines": "6.19.3"
+      },
+      "bin": {
+        "prisma": "build/index.js"
+      },
+      "engines": {
+        "node": ">=18.18"
+      },
+      "peerDependencies": {
+        "typescript": ">=5.1.0"
+      },
+      "peerDependenciesMeta": {
+        "typescript": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/prop-types": {
       "version": "15.8.1",
       "resolved": "https://registry.npmjs.org/prop-types/-/prop-types-15.8.1.tgz",
@@ -5223,6 +5776,21 @@
         "node": ">=6"
       }
     },
+    "node_modules/pure-rand": {
+      "version": "6.1.0",
+      "resolved": "https://registry.npmjs.org/pure-rand/-/pure-rand-6.1.0.tgz",
+      "integrity": "sha512-bVWawvoZoBYpp6yIoQtQXHZjmz35RSVHnUOTefl8Vcjr8snTPY1wnpSPMWekcFwbxI6gtmT7rSYPFvz71ldiOA==",
+      "funding": [
+        {
+          "type": "individual",
+          "url": "https://github.com/sponsors/dubzzz"
+        },
+        {
+          "type": "opencollective",
+          "url": "https://opencollective.com/fast-check"
+        }
+      ]
+    },
     "node_modules/queue-microtask": {
       "version": "1.2.3",
       "resolved": "https://registry.npmjs.org/queue-microtask/-/queue-microtask-1.2.3.tgz",
@@ -5243,6 +5811,15 @@
         }
       ]
     },
+    "node_modules/rc9": {
+      "version": "2.1.2",
+      "resolved": "https://registry.npmjs.org/rc9/-/rc9-2.1.2.tgz",
+      "integrity": "sha512-btXCnMmRIBINM2LDZoEmOogIZU7Qe7zn4BpomSKZ/ykbLObuBdvG+mFq11DL6fjH1DRwHhrlgtYWG96bJiC7Cg==",
+      "dependencies": {
+        "defu": "^6.1.4",
+        "destr": "^2.0.3"
+      }
+    },
     "node_modules/react": {
       "version": "19.2.8",
       "resolved": "https://registry.npmjs.org/react/-/react-19.2.8.tgz",
@@ -5268,6 +5845,18 @@
       "integrity": "sha512-24e6ynE2H+OKt4kqsOvNd8kBpV65zoxbA4BVsEOB3ARVWQki/DHzaUoC5KuON/BiccDaCCTZBuOcfZs70kR8bQ==",
       "dev": true
     },
+    "node_modules/readdirp": {
+      "version": "4.1.2",
+      "resolved": "https://registry.npmjs.org/readdirp/-/readdirp-4.1.2.tgz",
+      "integrity": "sha512-GDhwkLfywWL2s6vEjyhri+eXmfH6j1L7JE27WhqLeYzoh/A3DBaYGEj2H/HFZCn/kMfim73FXxEJTw06WtxQwg==",
+      "engines": {
+        "node": ">= 14.18.0"
+      },
+      "funding": {
+        "type": "individual",
+        "url": "https://paulmillr.com/funding/"
+      }
+    },
     "node_modules/reflect.getprototypeof": {
       "version": "1.0.10",
       "resolved": "https://registry.npmjs.org/reflect.getprototypeof/-/reflect.getprototypeof-1.0.10.tgz",
@@ -5871,6 +6460,14 @@
         "url": "https://opencollective.com/webpack"
       }
     },
+    "node_modules/tinyexec": {
+      "version": "1.3.0",
+      "resolved": "https://registry.npmjs.org/tinyexec/-/tinyexec-1.3.0.tgz",
+      "integrity": "sha512-QKAl9m8gWWGHV8jZcPeym6j+XULi6tOf1mT83WYJ4Lk2ytW/uwAWkrP0uFsdoYMdueVJ0qs26wZ+23xeB4ibNQ==",
+      "engines": {
+        "node": ">=18"
+      }
+    },
     "node_modules/tinyglobby": {
       "version": "0.2.17",
       "resolved": "https://registry.npmjs.org/tinyglobby/-/tinyglobby-0.2.17.tgz",
@@ -6191,6 +6788,18 @@
         "punycode": "^2.1.0"
       }
     },
+    "node_modules/uuid": {
+      "version": "14.0.2",
+      "resolved": "https://registry.npmjs.org/uuid/-/uuid-14.0.2.tgz",
+      "integrity": "sha512-xZe/16rV4aa+HGSOCiY2YeLT1OybRLrrkL/Rqaq7p7GMVXjFh+6wN4oMYgjFmnSnhY8t6Xpdl2l9qmnHYuMHwQ==",
+      "funding": [
+        "https://github.com/sponsors/broofa",
+        "https://github.com/sponsors/ctavan"
+      ],
+      "bin": {
+        "uuid": "dist-node/bin/uuid"
+      }
+    },
     "node_modules/which": {
       "version": "2.0.2",
       "resolved": "https://registry.npmjs.org/which/-/which-2.0.2.tgz",

package.json

@@ -6,18 +6,30 @@
     "dev": "next dev",
     "build": "next build",
     "start": "next start",
-    "lint": "eslint"
+    "lint": "eslint",
+    "dev:sqlite": "set DATABASE_URL=file:./prisma/dev.db && next dev"
   },
   "dependencies": {
+    "@dnd-kit/core": "^6.3.1",
+    "@dnd-kit/sortable": "^10.0.0",
+    "@dnd-kit/utilities": "^3.2.2",
+    "@prisma/client": "^6.19.3",
+    "bcryptjs": "^3.0.3",
+    "csv-parse": "^7.0.2",
     "next": "16.3.1",
+    "next-auth": "^4.24.15",
+    "prisma": "^6.19.3",
     "react": "19.2.8",
-    "react-dom": "19.2.8"
+    "react-dom": "19.2.8",
+    "uuid": "^14.0.2"
   },
   "devDependencies": {
     "@tailwindcss/postcss": "^4",
+    "@types/bcryptjs": "^3.0.0",
     "@types/node": "^20",
     "@types/react": "^19",
     "@types/react-dom": "^19",
+    "@types/uuid": "^11.0.0",
     "eslint": "^9",
     "eslint-config-next": "16.3.1",
     "tailwindcss": "^4",

prisma/dev/schema.prisma

@@ -0,0 +1,88 @@
+generator client {
+  provider = "prisma-client-js"
+}
+
+datasource db {
+  provider = "sqlite"
+  url      = env("DATABASE_URL")
+}
+
+model User {
+  id            String    @id @default(cuid())
+  email         String    @unique
+  name          String
+  passwordHash  String
+  avatarColor   String    @default("#4B7BF5")
+  createdAt     DateTime  @default(now())
+  updatedAt     DateTime  @updatedAt
+  lists         List[]
+  tasks         Task[]
+  tags          Tag[]
+  sessions      Session[]
+}
+
+model Session {
+  id        String   @id @default(cuid())
+  userId    String
+  token     String   @unique
+  expiresAt DateTime
+  createdAt DateTime @default(now())
+  user User @relation(fields: [userId], references: [id], onDelete: Cascade)
+}
+
+model List {
+  id        String   @id @default(cuid())
+  userId    String
+  name      String
+  color     String   @default("#4B7BF5")
+  icon      String   @default("list")
+  sortOrder Int      @default(0)
+  createdAt DateTime @default(now())
+  updatedAt DateTime @updatedAt
+  user  User   @relation(fields: [userId], references: [id], onDelete: Cascade)
+  tasks Task[]
+  @@index([userId])
+}
+
+model Task {
+  id          String    @id @default(cuid())
+  userId      String
+  listId      String
+  parentId    String?
+  title       String
+  note        String?
+  completed   Boolean   @default(false)
+  completedAt DateTime?
+  dueDate     DateTime?
+  priority    Int       @default(0)
+  sortOrder   Int       @default(0)
+  createdAt   DateTime  @default(now())
+  updatedAt   DateTime  @updatedAt
+  user     User   @relation(fields: [userId], references: [id], onDelete: Cascade)
+  list     List   @relation(fields: [listId], references: [id], onDelete: Cascade)
+  parent   Task?  @relation("TaskChildren", fields: [parentId], references: [id], onDelete: Cascade)
+  children Task[] @relation("TaskChildren")
+  tags     TaskTag[]
+  @@index([userId])
+  @@index([listId])
+  @@index([parentId])
+}
+
+model Tag {
+  id     String @id @default(cuid())
+  userId String
+  name   String
+  color  String @default("#6B6B6B")
+  user  User      @relation(fields: [userId], references: [id], onDelete: Cascade)
+  tasks TaskTag[]
+  @@unique([userId, name])
+  @@index([userId])
+}
+
+model TaskTag {
+  taskId String
+  tagId  String
+  task Task @relation(fields: [taskId], references: [id], onDelete: Cascade)
+  tag  Tag  @relation(fields: [tagId], references: [id], onDelete: Cascade)
+  @@id([taskId, tagId])
+}

prisma/migrations/20240101000000_init/migration.sql

@@ -0,0 +1,88 @@
+-- CreateTable
+CREATE TABLE "User" (
+    "id" TEXT NOT NULL,
+    "email" TEXT NOT NULL,
+    "name" TEXT NOT NULL,
+    "passwordHash" TEXT NOT NULL,
+    "avatarColor" TEXT NOT NULL DEFAULT '#4B7BF5',
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL,
+    CONSTRAINT "User_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "Session" (
+    "id" TEXT NOT NULL,
+    "userId" TEXT NOT NULL,
+    "token" TEXT NOT NULL,
+    "expiresAt" TIMESTAMP(3) NOT NULL,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    CONSTRAINT "Session_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "List" (
+    "id" TEXT NOT NULL,
+    "userId" TEXT NOT NULL,
+    "name" TEXT NOT NULL,
+    "color" TEXT NOT NULL DEFAULT '#4B7BF5',
+    "icon" TEXT NOT NULL DEFAULT 'list',
+    "sortOrder" INTEGER NOT NULL DEFAULT 0,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL,
+    CONSTRAINT "List_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "Task" (
+    "id" TEXT NOT NULL,
+    "userId" TEXT NOT NULL,
+    "listId" TEXT NOT NULL,
+    "parentId" TEXT,
+    "title" TEXT NOT NULL,
+    "note" TEXT,
+    "completed" BOOLEAN NOT NULL DEFAULT false,
+    "completedAt" TIMESTAMP(3),
+    "dueDate" TIMESTAMP(3),
+    "priority" INTEGER NOT NULL DEFAULT 0,
+    "sortOrder" INTEGER NOT NULL DEFAULT 0,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL,
+    CONSTRAINT "Task_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "Tag" (
+    "id" TEXT NOT NULL,
+    "userId" TEXT NOT NULL,
+    "name" TEXT NOT NULL,
+    "color" TEXT NOT NULL DEFAULT '#6B6B6B',
+    CONSTRAINT "Tag_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateTable
+CREATE TABLE "TaskTag" (
+    "taskId" TEXT NOT NULL,
+    "tagId" TEXT NOT NULL,
+    CONSTRAINT "TaskTag_pkey" PRIMARY KEY ("taskId","tagId")
+);
+
+-- CreateIndex
+CREATE UNIQUE INDEX "User_email_key" ON "User"("email");
+CREATE UNIQUE INDEX "Session_token_key" ON "Session"("token");
+CREATE UNIQUE INDEX "Tag_userId_name_key" ON "Tag"("userId", "name");
+CREATE INDEX "List_userId_idx" ON "List"("userId");
+CREATE INDEX "Task_userId_idx" ON "Task"("userId");
+CREATE INDEX "Task_listId_idx" ON "Task"("listId");
+CREATE INDEX "Task_parentId_idx" ON "Task"("parentId");
+CREATE INDEX "Tag_userId_idx" ON "Tag"("userId");
+
+-- AddForeignKey
+ALTER TABLE "Session" ADD CONSTRAINT "Session_userId_fkey" FOREIGN KEY ("userId") REFERENCES "User"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+ALTER TABLE "List" ADD CONSTRAINT "List_userId_fkey" FOREIGN KEY ("userId") REFERENCES "User"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+ALTER TABLE "Task" ADD CONSTRAINT "Task_userId_fkey" FOREIGN KEY ("userId") REFERENCES "User"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+ALTER TABLE "Task" ADD CONSTRAINT "Task_listId_fkey" FOREIGN KEY ("listId") REFERENCES "List"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+ALTER TABLE "Task" ADD CONSTRAINT "Task_parentId_fkey" FOREIGN KEY ("parentId") REFERENCES "Task"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+ALTER TABLE "Tag" ADD CONSTRAINT "Tag_userId_fkey" FOREIGN KEY ("userId") REFERENCES "User"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+ALTER TABLE "TaskTag" ADD CONSTRAINT "TaskTag_taskId_fkey" FOREIGN KEY ("taskId") REFERENCES "Task"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+ALTER TABLE "TaskTag" ADD CONSTRAINT "TaskTag_tagId_fkey" FOREIGN KEY ("tagId") REFERENCES "Tag"("id") ON DELETE CASCADE ON UPDATE CASCADE;

prisma/migrations/migration_lock.toml

@@ -0,0 +1,2 @@
+# Please do not edit this file manually
+provider = "postgresql"

prisma/schema.prisma

@@ -0,0 +1,101 @@
+generator client {
+  provider = "prisma-client-js"
+}
+
+datasource db {
+  provider = "postgresql"
+  url      = env("DATABASE_URL")
+}
+
+model User {
+  id            String    @id @default(cuid())
+  email         String    @unique
+  name          String
+  passwordHash  String
+  avatarColor   String    @default("#4B7BF5")
+  createdAt     DateTime  @default(now())
+  updatedAt     DateTime  @updatedAt
+
+  lists         List[]
+  tasks         Task[]
+  tags          Tag[]
+  sessions      Session[]
+}
+
+model Session {
+  id        String   @id @default(cuid())
+  userId    String
+  token     String   @unique
+  expiresAt DateTime
+  createdAt DateTime @default(now())
+
+  user User @relation(fields: [userId], references: [id], onDelete: Cascade)
+}
+
+model List {
+  id        String   @id @default(cuid())
+  userId    String
+  name      String
+  color     String   @default("#4B7BF5")
+  icon      String   @default("list")
+  sortOrder Int      @default(0)
+  createdAt DateTime @default(now())
+  updatedAt DateTime @updatedAt
+
+  user  User   @relation(fields: [userId], references: [id], onDelete: Cascade)
+  tasks Task[]
+
+  @@index([userId])
+}
+
+model Task {
+  id          String    @id @default(cuid())
+  userId      String
+  listId      String
+  parentId    String?
+
+  title       String
+  note        String?   @db.Text
+  completed   Boolean   @default(false)
+  completedAt DateTime?
+
+  dueDate     DateTime?
+  priority    Int       @default(0)
+  sortOrder   Int       @default(0)
+
+  createdAt   DateTime  @default(now())
+  updatedAt   DateTime  @updatedAt
+
+  user     User   @relation(fields: [userId], references: [id], onDelete: Cascade)
+  list     List   @relation(fields: [listId], references: [id], onDelete: Cascade)
+  parent   Task?  @relation("TaskChildren", fields: [parentId], references: [id], onDelete: Cascade)
+  children Task[] @relation("TaskChildren")
+  tags     TaskTag[]
+
+  @@index([userId])
+  @@index([listId])
+  @@index([parentId])
+}
+
+model Tag {
+  id     String @id @default(cuid())
+  userId String
+  name   String
+  color  String @default("#6B6B6B")
+
+  user  User      @relation(fields: [userId], references: [id], onDelete: Cascade)
+  tasks TaskTag[]
+
+  @@unique([userId, name])
+  @@index([userId])
+}
+
+model TaskTag {
+  taskId String
+  tagId  String
+
+  task Task @relation(fields: [taskId], references: [id], onDelete: Cascade)
+  tag  Tag  @relation(fields: [tagId], references: [id], onDelete: Cascade)
+
+  @@id([taskId, tagId])
+}

public/icons/icon-192.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><rect width="100" height="100" rx="20" fill="#4B7BF5"/><text x="50" y="67" font-family="Arial" font-size="55" font-weight="bold" fill="white" text-anchor="middle">&#x2713;</text></svg>

public/icons/icon-512.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><rect width="100" height="100" rx="20" fill="#4B7BF5"/><text x="50" y="67" font-family="Arial" font-size="55" font-weight="bold" fill="white" text-anchor="middle">&#x2713;</text></svg>

public/icons/icon.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><rect width="100" height="100" rx="20" fill="#4B7BF5"/><text x="50" y="67" font-family="Arial" font-size="55" font-weight="bold" fill="white" text-anchor="middle">&#x2713;</text></svg>

public/manifest.json

@@ -0,0 +1 @@
+{"name":"CheckFlow","short_name":"CheckFlow","description":"Clean, fast self-hosted todo app","start_url":"/","display":"standalone","background_color":"#FFFFFF","theme_color":"#4B7BF5","orientation":"any","icons":[{"src":"/icons/icon.svg","sizes":"any","type":"image/svg+xml","purpose":"any maskable"}],"categories":["productivity","utilities"],"lang":"ko"}

public/sw.js

@@ -0,0 +1,34 @@
+const CACHE_NAME = "checkflow-v1";
+const STATIC_ASSETS = ["/", "/login", "/register", "/manifest.json", "/icons/icon.svg"];
+
+self.addEventListener("install", (event) => {
+  event.waitUntil(
+    caches.open(CACHE_NAME).then((cache) => cache.addAll(STATIC_ASSETS))
+  );
+  self.skipWaiting();
+});
+
+self.addEventListener("activate", (event) => {
+  event.waitUntil(
+    caches.keys().then((keys) =>
+      Promise.all(keys.filter((k) => k !== CACHE_NAME).map((k) => caches.delete(k)))
+    )
+  );
+  self.clients.claim();
+});
+
+self.addEventListener("fetch", (event) => {
+  const { request } = event;
+  const url = new URL(request.url);
+
+  // Network-first for API
+  if (url.pathname.startsWith("/api")) {
+    event.respondWith(fetch(request).catch(() => new Response(JSON.stringify({ error: "Offline" }), { headers: { "Content-Type": "application/json" } })));
+    return;
+  }
+
+  // Cache-first for static
+  event.respondWith(
+    caches.match(request).then((cached) => cached || fetch(request))
+  );
+});

src/app/api/auth/[...nextauth]/route.ts

@@ -0,0 +1,5 @@
+import NextAuth from "next-auth";
+import { authOptions } from "@/lib/auth";
+
+const handler = NextAuth(authOptions);
+export { handler as GET, handler as POST };

src/app/api/auth/register/route.ts

@@ -0,0 +1,49 @@
+import { NextRequest, NextResponse } from "next/server";
+import { prisma } from "@/lib/prisma";
+import bcrypt from "bcryptjs";
+
+export async function POST(req: NextRequest) {
+  try {
+    const body = await req.json().catch(() => null);
+    if (!body) {
+      return NextResponse.json({ error: "Invalid request body" }, { status: 400 });
+    }
+    const { name, email, password } = body;
+
+    if (!name || !email || !password) {
+      return NextResponse.json({ error: "All fields required" }, { status: 400 });
+    }
+    if (password.length < 8) {
+      return NextResponse.json({ error: "Password must be at least 8 characters" }, { status: 400 });
+    }
+
+    const existing = await prisma.user.findUnique({ where: { email } });
+    if (existing) {
+      return NextResponse.json({ error: "Email already in use" }, { status: 409 });
+    }
+
+    const passwordHash = await bcrypt.hash(password, 12);
+    const user = await prisma.user.create({
+      data: { name, email, passwordHash },
+    });
+
+    // Create default list
+    await prisma.list.create({
+      data: {
+        userId: user.id,
+        name: "My Tasks",
+        color: "#4B7BF5",
+        icon: "inbox",
+        sortOrder: 0,
+      },
+    });
+
+    return NextResponse.json({ id: user.id, email: user.email, name: user.name }, { status: 201 });
+  } catch (err) {
+    console.error("[register]", err);
+    return NextResponse.json(
+      { error: "Server error. Make sure the database is running." },
+      { status: 500 }
+    );
+  }
+}

src/app/api/dav/[...path]/route.ts

@@ -0,0 +1,77 @@
+import { NextRequest, NextResponse } from "next/server";
+import { prisma } from "@/lib/prisma";
+import bcrypt from "bcryptjs";
+
+async function authenticate(req: NextRequest) {
+  const authHeader = req.headers.get("authorization");
+  if (!authHeader?.startsWith("Basic ")) return null;
+  const decoded = Buffer.from(authHeader.slice(6), "base64").toString();
+  const [email, password] = decoded.split(":");
+  const user = await prisma.user.findUnique({ where: { email } });
+  if (!user) return null;
+  const valid = await bcrypt.compare(password, user.passwordHash);
+  return valid ? user : null;
+}
+
+function taskToVTodo(task: { id: string; title: string; note: string | null; completed: boolean; completedAt: Date | null; dueDate: Date | null; priority: number; createdAt: Date; updatedAt: Date }) {
+  const now = new Date().toISOString().replace(/[-:]/g, "").split(".")[0] + "Z";
+  const priorityMap: Record<number, number> = { 0: 0, 1: 9, 2: 5, 3: 1 };
+  let vtodo = [
+    "BEGIN:VTODO",
+    `UID:${task.id}@checkflow`,
+    `DTSTAMP:${now}`,
+    `CREATED:${task.createdAt.toISOString().replace(/[-:]/g, "").split(".")[0] + "Z"}`,
+    `LAST-MODIFIED:${task.updatedAt.toISOString().replace(/[-:]/g, "").split(".")[0] + "Z"}`,
+    `SUMMARY:${task.title.replace(/\n/g, "\\n")}`,
+    `STATUS:${task.completed ? "COMPLETED" : "NEEDS-ACTION"}`,
+    `PRIORITY:${priorityMap[task.priority] ?? 0}`,
+  ];
+  if (task.note) vtodo.push(`DESCRIPTION:${task.note.replace(/\n/g, "\\n")}`);
+  if (task.dueDate) vtodo.push(`DUE:${task.dueDate.toISOString().replace(/[-:]/g, "").split(".")[0] + "Z"}`);
+  if (task.completedAt) vtodo.push(`COMPLETED:${task.completedAt.toISOString().replace(/[-:]/g, "").split(".")[0] + "Z"}`);
+  vtodo.push("END:VTODO");
+  return vtodo.join("\r\n");
+}
+
+// Handle all CalDAV/CardDAV requests
+export async function GET(req: NextRequest) {
+  const user = await authenticate(req);
+  if (!user) {
+    return new NextResponse("Unauthorized", {
+      status: 401,
+      headers: { "WWW-Authenticate": 'Basic realm="CheckFlow"' },
+    });
+  }
+
+  const tasks = await prisma.task.findMany({
+    where: { userId: user.id, parentId: null },
+    orderBy: { sortOrder: "asc" },
+  });
+
+  const icsContent = [
+    "BEGIN:VCALENDAR",
+    "VERSION:2.0",
+    "PRODID:-//CheckFlow//CheckFlow//EN",
+    "CALSCALE:GREGORIAN",
+    "METHOD:PUBLISH",
+    ...tasks.map(taskToVTodo),
+    "END:VCALENDAR",
+  ].join("\r\n");
+
+  return new NextResponse(icsContent, {
+    headers: {
+      "Content-Type": "text/calendar; charset=utf-8",
+      "Content-Disposition": "attachment; filename=checkflow.ics",
+    },
+  });
+}
+
+// OPTIONS for CORS
+export async function OPTIONS() {
+  return new NextResponse(null, {
+    headers: {
+      Allow: "GET, OPTIONS",
+      "DAV": "1, 2, calendar-access",
+    },
+  });
+}

src/app/api/import/route.ts

@@ -0,0 +1,132 @@
+import { NextRequest, NextResponse } from "next/server";
+import { getServerSession } from "next-auth";
+import { authOptions } from "@/lib/auth";
+import { prisma } from "@/lib/prisma";
+
+// TickTick CSV import
+export async function POST(req: NextRequest) {
+  const session = await getServerSession(authOptions);
+  if (!session) return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+
+  const formData = await req.formData();
+  const file = formData.get("file") as File | null;
+  const listId = formData.get("listId") as string | null;
+
+  if (!file || !listId) {
+    return NextResponse.json({ error: "file and listId required" }, { status: 400 });
+  }
+
+  const list = await prisma.list.findFirst({ where: { id: listId, userId: session.user.id } });
+  if (!list) return NextResponse.json({ error: "List not found" }, { status: 404 });
+
+  const text = await file.text();
+  const ext = file.name.split(".").pop()?.toLowerCase();
+
+  let imported = 0;
+
+  if (ext === "csv") {
+    const lines = text.split("\n");
+    const header = lines[0].split(",").map((h) => h.trim().replace(/"/g, ""));
+    const titleIdx = header.findIndex((h) => h.toLowerCase().includes("title") || h.toLowerCase().includes("content"));
+    const noteIdx = header.findIndex((h) => h.toLowerCase().includes("note") || h.toLowerCase().includes("description"));
+    const dueIdx = header.findIndex((h) => h.toLowerCase().includes("due"));
+    const priorityIdx = header.findIndex((h) => h.toLowerCase().includes("priority"));
+    const completedIdx = header.findIndex((h) => h.toLowerCase().includes("status") || h.toLowerCase().includes("completed"));
+
+    const priorityMap: Record<string, number> = { high: 3, medium: 2, low: 1, none: 0, "3": 3, "2": 2, "1": 1, "0": 0 };
+
+    for (let i = 1; i < lines.length; i++) {
+      const line = lines[i].trim();
+      if (!line) continue;
+
+      // Handle quoted CSV fields
+      const fields: string[] = [];
+      let inQuotes = false;
+      let current = "";
+      for (const ch of line + ",") {
+        if (ch === '"') { inQuotes = !inQuotes; }
+        else if (ch === "," && !inQuotes) { fields.push(current.trim()); current = ""; }
+        else { current += ch; }
+      }
+
+      const title = titleIdx >= 0 ? fields[titleIdx]?.replace(/"/g, "") : "";
+      if (!title) continue;
+
+      const note = noteIdx >= 0 ? fields[noteIdx]?.replace(/"/g, "") : null;
+      const dueRaw = dueIdx >= 0 ? fields[dueIdx] : null;
+      const priorityRaw = priorityIdx >= 0 ? fields[priorityIdx]?.toLowerCase() : "0";
+      const completedRaw = completedIdx >= 0 ? fields[completedIdx]?.toLowerCase() : "";
+
+      let dueDate: Date | null = null;
+      if (dueRaw) {
+        const d = new Date(dueRaw);
+        if (!isNaN(d.getTime())) dueDate = d;
+      }
+
+      const priority = priorityMap[priorityRaw || "0"] ?? 0;
+      const completed = completedRaw === "completed" || completedRaw === "true" || completedRaw === "1";
+
+      await prisma.task.create({
+        data: {
+          userId: session.user.id,
+          listId,
+          title,
+          note: note || null,
+          dueDate,
+          priority,
+          completed,
+          completedAt: completed ? new Date() : null,
+          sortOrder: imported,
+        },
+      });
+      imported++;
+    }
+  } else if (ext === "ics") {
+    // Parse ICS / iCalendar VTODO
+    const todos = text.split("BEGIN:VTODO").slice(1);
+    for (const todo of todos) {
+      const get = (key: string) => {
+        const match = todo.match(new RegExp(`^${key}[^:]*:(.*)$`, "m"));
+        return match ? match[1].trim().replace(/\\n/g, "\n") : null;
+      };
+      const title = get("SUMMARY");
+      if (!title) continue;
+      const note = get("DESCRIPTION");
+      const dueDateRaw = get("DUE") || get("DTSTART");
+      let dueDate: Date | null = null;
+      if (dueDateRaw) {
+        const d = new Date(dueDateRaw.replace(/(\d{4})(\d{2})(\d{2})/, "$1-$2-$3"));
+        if (!isNaN(d.getTime())) dueDate = d;
+      }
+      const statusRaw = get("STATUS");
+      const completed = statusRaw === "COMPLETED";
+      const priorityRaw = get("PRIORITY");
+      let priority = 0;
+      if (priorityRaw) {
+        const p = parseInt(priorityRaw);
+        if (p >= 1 && p <= 3) priority = 4 - p; // ICS: 1=high, ours: 3=high
+        else if (p >= 4 && p <= 6) priority = 2;
+        else if (p >= 7) priority = 1;
+      }
+
+      await prisma.task.create({
+        data: {
+          userId: session.user.id,
+          listId,
+          title,
+          note: note || null,
+          dueDate,
+          priority,
+          completed,
+          completedAt: completed ? new Date() : null,
+          sortOrder: imported,
+        },
+      });
+      imported++;
+    }
+  } else {
+    return NextResponse.json({ error: "Unsupported file format. Use CSV or ICS." }, { status: 400 });
+  }
+
+  return NextResponse.json({ imported });
+}

src/app/api/lists/[id]/route.ts

@@ -0,0 +1,49 @@
+import { NextRequest, NextResponse } from "next/server";
+import { getServerSession } from "next-auth";
+import { authOptions } from "@/lib/auth";
+import { prisma } from "@/lib/prisma";
+
+type Ctx = { params: Promise<{ id: string }> };
+
+export async function PATCH(req: NextRequest, { params }: Ctx) {
+  try {
+    const session = await getServerSession(authOptions);
+    if (!session) return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+    const { id } = await params;
+
+    const body = await req.json().catch(() => null);
+    if (!body) return NextResponse.json({ error: "Invalid body" }, { status: 400 });
+
+    const list = await prisma.list.findFirst({ where: { id, userId: session.user.id } });
+    if (!list) return NextResponse.json({ error: "Not found" }, { status: 404 });
+
+    const allowed = ["name", "color", "icon", "sortOrder"];
+    const data: Record<string, unknown> = {};
+    for (const key of allowed) {
+      if (key in body) data[key] = body[key];
+    }
+
+    const updated = await prisma.list.update({ where: { id }, data });
+    return NextResponse.json(updated);
+  } catch (err) {
+    console.error("[lists/id:PATCH]", err);
+    return NextResponse.json({ error: "Failed to update list" }, { status: 500 });
+  }
+}
+
+export async function DELETE(_: NextRequest, { params }: Ctx) {
+  try {
+    const session = await getServerSession(authOptions);
+    if (!session) return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+    const { id } = await params;
+
+    const list = await prisma.list.findFirst({ where: { id, userId: session.user.id } });
+    if (!list) return NextResponse.json({ error: "Not found" }, { status: 404 });
+
+    await prisma.list.delete({ where: { id } });
+    return NextResponse.json({ ok: true });
+  } catch (err) {
+    console.error("[lists/id:DELETE]", err);
+    return NextResponse.json({ error: "Failed to delete list" }, { status: 500 });
+  }
+}

src/app/api/lists/route.ts

@@ -0,0 +1,51 @@
+import { NextRequest, NextResponse } from "next/server";
+import { getServerSession } from "next-auth";
+import { authOptions } from "@/lib/auth";
+import { prisma } from "@/lib/prisma";
+
+export async function GET() {
+  try {
+    const session = await getServerSession(authOptions);
+    if (!session) return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+
+    const lists = await prisma.list.findMany({
+      where: { userId: session.user.id },
+      orderBy: { sortOrder: "asc" },
+      include: {
+        _count: { select: { tasks: { where: { completed: false, parentId: null } } } },
+      },
+    });
+    return NextResponse.json(lists);
+  } catch (err) {
+    console.error("[lists:GET]", err);
+    return NextResponse.json({ error: "Failed to fetch lists" }, { status: 500 });
+  }
+}
+
+export async function POST(req: NextRequest) {
+  try {
+    const session = await getServerSession(authOptions);
+    if (!session) return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+
+    const body = await req.json().catch(() => null);
+    if (!body) return NextResponse.json({ error: "Invalid body" }, { status: 400 });
+
+    const { name, color, icon } = body;
+    if (!name?.trim()) return NextResponse.json({ error: "Name required" }, { status: 400 });
+
+    const count = await prisma.list.count({ where: { userId: session.user.id } });
+    const list = await prisma.list.create({
+      data: {
+        userId: session.user.id,
+        name: name.trim(),
+        color: color || "#4B7BF5",
+        icon: icon || "list",
+        sortOrder: count,
+      },
+    });
+    return NextResponse.json(list, { status: 201 });
+  } catch (err) {
+    console.error("[lists:POST]", err);
+    return NextResponse.json({ error: "Failed to create list" }, { status: 500 });
+  }
+}

src/app/api/tasks/[id]/route.ts

@@ -0,0 +1,81 @@
+import { NextRequest, NextResponse } from "next/server";
+import { getServerSession } from "next-auth";
+import { authOptions } from "@/lib/auth";
+import { prisma } from "@/lib/prisma";
+
+type Ctx = { params: Promise<{ id: string }> };
+
+export async function GET(_: NextRequest, { params }: Ctx) {
+  try {
+    const session = await getServerSession(authOptions);
+    if (!session) return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+    const { id } = await params;
+
+    const task = await prisma.task.findFirst({
+      where: { id, userId: session.user.id },
+      include: { children: { orderBy: { sortOrder: "asc" } }, tags: { include: { tag: true } } },
+    });
+    if (!task) return NextResponse.json({ error: "Not found" }, { status: 404 });
+    return NextResponse.json(task);
+  } catch (err) {
+    console.error("[tasks/id:GET]", err);
+    return NextResponse.json({ error: "Failed to fetch task" }, { status: 500 });
+  }
+}
+
+export async function PATCH(req: NextRequest, { params }: Ctx) {
+  try {
+    const session = await getServerSession(authOptions);
+    if (!session) return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+    const { id } = await params;
+
+    const body = await req.json().catch(() => null);
+    if (!body) return NextResponse.json({ error: "Invalid body" }, { status: 400 });
+
+    const task = await prisma.task.findFirst({ where: { id, userId: session.user.id } });
+    if (!task) return NextResponse.json({ error: "Not found" }, { status: 404 });
+
+    // Sanitize allowed fields
+    const allowed = ["title", "note", "completed", "completedAt", "dueDate", "priority", "sortOrder", "listId"];
+    const data: Record<string, unknown> = {};
+    for (const key of allowed) {
+      if (key in body) data[key] = body[key];
+    }
+
+    // Auto-set completedAt
+    if ("completed" in data) {
+      data.completedAt = data.completed ? new Date() : null;
+    }
+    // Convert dueDate string to Date
+    if ("dueDate" in data) {
+      data.dueDate = data.dueDate ? new Date(data.dueDate as string) : null;
+    }
+
+    const updated = await prisma.task.update({
+      where: { id },
+      data,
+      include: { children: { orderBy: { sortOrder: "asc" } }, tags: { include: { tag: true } } },
+    });
+    return NextResponse.json(updated);
+  } catch (err) {
+    console.error("[tasks/id:PATCH]", err);
+    return NextResponse.json({ error: "Failed to update task" }, { status: 500 });
+  }
+}
+
+export async function DELETE(_: NextRequest, { params }: Ctx) {
+  try {
+    const session = await getServerSession(authOptions);
+    if (!session) return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+    const { id } = await params;
+
+    const task = await prisma.task.findFirst({ where: { id, userId: session.user.id } });
+    if (!task) return NextResponse.json({ error: "Not found" }, { status: 404 });
+
+    await prisma.task.delete({ where: { id } });
+    return NextResponse.json({ ok: true });
+  } catch (err) {
+    console.error("[tasks/id:DELETE]", err);
+    return NextResponse.json({ error: "Failed to delete task" }, { status: 500 });
+  }
+}

src/app/api/tasks/route.ts

@@ -0,0 +1,70 @@
+import { NextRequest, NextResponse } from "next/server";
+import { getServerSession } from "next-auth";
+import { authOptions } from "@/lib/auth";
+import { prisma } from "@/lib/prisma";
+
+export async function GET(req: NextRequest) {
+  try {
+    const session = await getServerSession(authOptions);
+    if (!session) return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+
+    const { searchParams } = new URL(req.url);
+    const listId = searchParams.get("listId");
+    const showCompleted = searchParams.get("showCompleted") === "true";
+
+    const where: Record<string, unknown> = {
+      userId: session.user.id,
+      parentId: null,
+      ...(listId ? { listId } : {}),
+      ...(showCompleted ? {} : { completed: false }),
+    };
+
+    const tasks = await prisma.task.findMany({
+      where,
+      orderBy: [{ sortOrder: "asc" }, { createdAt: "asc" }],
+      include: {
+        children: { orderBy: [{ sortOrder: "asc" }] },
+        tags: { include: { tag: true } },
+      },
+    });
+    return NextResponse.json(tasks);
+  } catch (err) {
+    console.error("[tasks:GET]", err);
+    return NextResponse.json({ error: "Failed to fetch tasks" }, { status: 500 });
+  }
+}
+
+export async function POST(req: NextRequest) {
+  try {
+    const session = await getServerSession(authOptions);
+    if (!session) return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+
+    const body = await req.json().catch(() => null);
+    if (!body) return NextResponse.json({ error: "Invalid body" }, { status: 400 });
+
+    const { title, listId, parentId, dueDate, priority, note } = body;
+    if (!title || !listId) return NextResponse.json({ error: "title and listId required" }, { status: 400 });
+
+    const list = await prisma.list.findFirst({ where: { id: listId, userId: session.user.id } });
+    if (!list) return NextResponse.json({ error: "List not found" }, { status: 404 });
+
+    const count = await prisma.task.count({ where: { listId, parentId: parentId || null } });
+    const task = await prisma.task.create({
+      data: {
+        userId: session.user.id,
+        listId,
+        parentId: parentId || null,
+        title: title.trim(),
+        note: note?.trim() || null,
+        dueDate: dueDate ? new Date(dueDate) : null,
+        priority: Number(priority) || 0,
+        sortOrder: count,
+      },
+      include: { children: true, tags: { include: { tag: true } } },
+    });
+    return NextResponse.json(task, { status: 201 });
+  } catch (err) {
+    console.error("[tasks:POST]", err);
+    return NextResponse.json({ error: "Failed to create task" }, { status: 500 });
+  }
+}

src/app/layout.tsx

@@ -1,29 +1,39 @@
-import type { Metadata } from "next";
+import type { Metadata, Viewport } from "next";
-import { Geist, Geist_Mono } from "next/font/google";
 import "./globals.css";
-
+import { Providers } from "./providers";
-const geistSans = Geist({
-  variable: "--font-geist-sans",
-  subsets: ["latin"],
-});
-
-const geistMono = Geist_Mono({
-  variable: "--font-geist-mono",
-  subsets: ["latin"],
-});
 
 export const metadata: Metadata = {
-  title: "Create Next App",
+  title: "CheckFlow — Your Personal Todo",
-  description: "Generated by create next app",
+  description: "A clean, fast, self-hosted todo app with hierarchical tasks and rich notes.",
+  manifest: "/manifest.json",
+  appleWebApp: {
+    capable: true,
+    statusBarStyle: "default",
+    title: "CheckFlow",
+  },
 };
 
-export default function RootLayout({ children }: LayoutProps<"/">) {
+export const viewport: Viewport = {
+  themeColor: "#4B7BF5",
+  width: "device-width",
+  initialScale: 1,
+  viewportFit: "cover",
+};
+
+export default function RootLayout({ children }: { children: React.ReactNode }) {
   return (
-    <html
+    <html lang="ko" suppressHydrationWarning>
-      lang="en"
+      <head>
-      className={`${geistSans.variable} ${geistMono.variable} h-full antialiased`}
+        <link rel="preconnect" href="https://fonts.googleapis.com" />
-    >
+        <link rel="preconnect" href="https://fonts.gstatic.com" crossOrigin="anonymous" />
-      <body className="min-h-full flex flex-col">{children}</body>
+        <link
+          href="https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&display=swap"
+          rel="stylesheet"
+        />
+      </head>
+      <body>
+        <Providers>{children}</Providers>
+      </body>
     </html>
   );
-}
+}

src/app/login/page.tsx

@@ -0,0 +1,74 @@
+"use client";
+import { useState } from "react";
+import { signIn } from "next-auth/react";
+import { useRouter } from "next/navigation";
+import Link from "next/link";
+
+export default function LoginPage() {
+  const router = useRouter();
+  const [email, setEmail] = useState("");
+  const [password, setPassword] = useState("");
+  const [error, setError] = useState("");
+  const [loading, setLoading] = useState(false);
+
+  const handleSubmit = async (e: React.FormEvent) => {
+    e.preventDefault();
+    setError("");
+    setLoading(true);
+    const res = await signIn("credentials", { email, password, redirect: false });
+    setLoading(false);
+    if (res?.error) {
+      setError("Invalid email or password.");
+    } else {
+      router.push("/");
+    }
+  };
+
+  return (
+    <div className="auth-page">
+      <div className="auth-card">
+        <div className="auth-logo">
+          <div className="auth-logo-icon">✓</div>
+          <span className="auth-logo-name">CheckFlow</span>
+        </div>
+        <h1 className="auth-title">Welcome back</h1>
+        <p className="auth-subtitle">Sign in to your account</p>
+        <form onSubmit={handleSubmit}>
+          <div className="form-group">
+            <label className="form-label">Email</label>
+            <input
+              id="email"
+              type="email"
+              className="form-input"
+              placeholder="you@example.com"
+              value={email}
+              onChange={(e) => setEmail(e.target.value)}
+              required
+              autoFocus
+            />
+          </div>
+          <div className="form-group">
+            <label className="form-label">Password</label>
+            <input
+              id="password"
+              type="password"
+              className="form-input"
+              placeholder="••••••••"
+              value={password}
+              onChange={(e) => setPassword(e.target.value)}
+              required
+            />
+          </div>
+          {error && <p className="form-error" style={{ marginBottom: "12px" }}>{error}</p>}
+          <button id="login-btn" type="submit" className="btn btn-primary w-full" disabled={loading} style={{ height: "44px" }}>
+            {loading ? "Signing in..." : "Sign in"}
+          </button>
+        </form>
+        <p className="auth-footer">
+          Don&apos;t have an account?{" "}
+          <Link href="/register" className="auth-link">Create one</Link>
+        </p>
+      </div>
+    </div>
+  );
+}

src/app/page.tsx

@@ -1,69 +1,10 @@
-import Image from "next/image";
+import { getServerSession } from "next-auth";
+import { redirect } from "next/navigation";
+import { authOptions } from "@/lib/auth";
+import { AppShell } from "@/components/layout/AppShell";
 
-export default function Home() {
+export default async function HomePage() {
-  return (
+  const session = await getServerSession(authOptions);
-    <div className="flex flex-col flex-1 items-center justify-center bg-zinc-50 font-sans dark:bg-black">
+  if (!session) redirect("/login");
-      <main className="flex flex-1 w-full max-w-3xl flex-col items-center justify-between py-32 px-16 bg-white dark:bg-black sm:items-start">
+  return <AppShell user={session.user} />;
-        <Image
+}
-          className="dark:invert h-5 w-[100px]"
-          src="/next.svg"
-          alt="Next.js logo"
-          width={100}
-          height={20}
-          priority
-        />
-        <div className="flex flex-col items-center gap-6 text-center sm:items-start sm:text-left">
-          <h1 className="max-w-xs text-3xl font-semibold leading-10 tracking-tight text-black dark:text-zinc-50">
-            To get started, edit the{" "}
-            <code className="rounded bg-black/[.06] px-1.5 py-0.5 font-mono text-[0.9em] dark:bg-white/[.08]">
-              page.tsx
-            </code>{" "}
-            file.
-          </h1>
-          <p className="max-w-md text-lg leading-8 text-zinc-600 dark:text-zinc-400">
-            Looking for a starting point or more instructions? Head over to{" "}
-            <a
-              href="https://vercel.com/templates?framework=next.js&utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-              className="font-medium text-zinc-950 dark:text-zinc-50"
-            >
-              Templates
-            </a>{" "}
-            or the{" "}
-            <a
-              href="https://nextjs.org/learn?utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-              className="font-medium text-zinc-950 dark:text-zinc-50"
-            >
-              Learning
-            </a>{" "}
-            center.
-          </p>
-        </div>
-        <div className="flex flex-col gap-4 text-base font-medium sm:flex-row">
-          <a
-            className="flex h-12 w-full items-center justify-center gap-2 rounded-full bg-foreground px-5 text-background transition-colors hover:bg-[#383838] dark:hover:bg-[#ccc] md:w-[158px]"
-            href="https://vercel.com/new?utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-            target="_blank"
-            rel="noopener noreferrer"
-          >
-            <Image
-              className="dark:invert h-[14px] w-4"
-              src="/vercel.svg"
-              alt="Vercel logomark"
-              width={16}
-              height={14}
-            />
-            Deploy Now
-          </a>
-          <a
-            className="flex h-12 w-full items-center justify-center rounded-full border border-solid border-black/[.08] px-5 transition-colors hover:border-transparent hover:bg-black/[.04] dark:border-white/[.145] dark:hover:bg-[#1a1a1a] md:w-[158px]"
-            href="https://nextjs.org/docs?utm_source=create-next-app&utm_medium=appdir-template-tw&utm_campaign=create-next-app"
-            target="_blank"
-            rel="noopener noreferrer"
-          >
-            Documentation
-          </a>
-        </div>
-      </main>
-    </div>
-  );
-}

src/app/providers.tsx

@@ -0,0 +1,43 @@
+"use client";
+import { SessionProvider } from "next-auth/react";
+import { useEffect } from "react";
+import { I18nProvider } from "@/lib/i18n";
+
+export type ThemeMode = "system" | "light" | "dark";
+
+export function applyTheme(mode: ThemeMode) {
+  const isDark =
+    mode === "dark" ||
+    (mode === "system" && window.matchMedia("(prefers-color-scheme: dark)").matches);
+  document.documentElement.setAttribute("data-theme", isDark ? "dark" : "light");
+  localStorage.setItem("theme", mode);
+}
+
+export function Providers({ children }: { children: React.ReactNode }) {
+  useEffect(() => {
+    // Apply saved theme
+    const saved = (localStorage.getItem("theme") as ThemeMode) || "system";
+    applyTheme(saved);
+
+    // Watch system preference changes (only affects "system" mode)
+    const mq = window.matchMedia("(prefers-color-scheme: dark)");
+    const onMqChange = () => {
+      const current = (localStorage.getItem("theme") as ThemeMode) || "system";
+      if (current === "system") applyTheme("system");
+    };
+    mq.addEventListener("change", onMqChange);
+
+    // Service Worker
+    if ("serviceWorker" in navigator) {
+      navigator.serviceWorker.register("/sw.js").catch(console.error);
+    }
+
+    return () => mq.removeEventListener("change", onMqChange);
+  }, []);
+
+  return (
+    <SessionProvider>
+      <I18nProvider>{children}</I18nProvider>
+    </SessionProvider>
+  );
+}

src/app/register/page.tsx

@@ -0,0 +1,103 @@
+"use client";
+import { useState } from "react";
+import { signIn } from "next-auth/react";
+import { useRouter } from "next/navigation";
+import Link from "next/link";
+
+export default function RegisterPage() {
+  const router = useRouter();
+  const [name, setName] = useState("");
+  const [email, setEmail] = useState("");
+  const [password, setPassword] = useState("");
+  const [error, setError] = useState("");
+  const [loading, setLoading] = useState(false);
+
+  const handleSubmit = async (e: React.FormEvent) => {
+    e.preventDefault();
+    setError("");
+    setLoading(true);
+
+    const res = await fetch("/api/auth/register", {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({ name, email, password }),
+    });
+
+    if (!res.ok) {
+      let msg = "Registration failed.";
+      try {
+        const data = await res.json();
+        msg = data.error || msg;
+      } catch {
+        // non-JSON response (e.g. 500 HTML page)
+      }
+      setError(msg);
+      setLoading(false);
+      return;
+    }
+
+    await signIn("credentials", { email, password, redirect: false });
+    router.push("/");
+  };
+
+  return (
+    <div className="auth-page">
+      <div className="auth-card">
+        <div className="auth-logo">
+          <div className="auth-logo-icon">✓</div>
+          <span className="auth-logo-name">CheckFlow</span>
+        </div>
+        <h1 className="auth-title">Create account</h1>
+        <p className="auth-subtitle">Start organizing your tasks today</p>
+        <form onSubmit={handleSubmit}>
+          <div className="form-group">
+            <label className="form-label">Display Name</label>
+            <input
+              id="name"
+              type="text"
+              className="form-input"
+              placeholder="Your name"
+              value={name}
+              onChange={(e) => setName(e.target.value)}
+              required
+              autoFocus
+            />
+          </div>
+          <div className="form-group">
+            <label className="form-label">Email</label>
+            <input
+              id="reg-email"
+              type="email"
+              className="form-input"
+              placeholder="you@example.com"
+              value={email}
+              onChange={(e) => setEmail(e.target.value)}
+              required
+            />
+          </div>
+          <div className="form-group">
+            <label className="form-label">Password</label>
+            <input
+              id="reg-password"
+              type="password"
+              className="form-input"
+              placeholder="Min. 8 characters"
+              value={password}
+              onChange={(e) => setPassword(e.target.value)}
+              required
+              minLength={8}
+            />
+          </div>
+          {error && <p className="form-error" style={{ marginBottom: "12px" }}>{error}</p>}
+          <button id="register-btn" type="submit" className="btn btn-primary w-full" disabled={loading} style={{ height: "44px" }}>
+            {loading ? "Creating account..." : "Create account"}
+          </button>
+        </form>
+        <p className="auth-footer">
+          Already have an account?{" "}
+          <Link href="/login" className="auth-link">Sign in</Link>
+        </p>
+      </div>
+    </div>
+  );
+}

src/components/layout/AppShell.tsx

@@ -0,0 +1,106 @@
+"use client";
+import { useState, useCallback } from "react";
+import { Sidebar } from "./Sidebar";
+import { TaskList } from "../tasks/TaskList";
+import { TaskDetail } from "../tasks/TaskDetail";
+
+interface User { id: string; name?: string | null; email?: string | null; }
+interface List { id: string; name: string; color: string; icon: string; _count?: { tasks: number } }
+interface Task {
+  id: string; listId: string; parentId: string | null; title: string; note: string | null;
+  completed: boolean; completedAt: string | null; dueDate: string | null; priority: number;
+  sortOrder: number; createdAt: string; updatedAt: string;
+  children: Task[]; tags: { tag: { id: string; name: string; color: string } }[];
+}
+
+export function AppShell({ user }: { user: User }) {
+  const [lists, setLists] = useState<List[]>([]);
+  const [selectedListId, setSelectedListId] = useState<string | null>(null);
+  const [selectedTask, setSelectedTask] = useState<Task | null>(null);
+  const [tasks, setTasks] = useState<Task[]>([]);
+  const [sidebarOpen, setSidebarOpen] = useState(false);
+  const [showCompleted, setShowCompleted] = useState(false);
+  const [refreshKey, setRefreshKey] = useState(0);
+
+  const refresh = useCallback(() => setRefreshKey((k) => k + 1), []);
+
+  const handleTaskSelect = useCallback((task: Task | null) => {
+    setSelectedTask(task);
+  }, []);
+
+  const handleTaskUpdate = useCallback((updated: Task) => {
+    setTasks((prev) => prev.map((t) => (t.id === updated.id ? updated : t)));
+    setSelectedTask(updated);
+  }, []);
+
+  const handleListSelect = useCallback((id: string) => {
+    setSelectedListId(id);
+    setSelectedTask(null);
+    setSidebarOpen(false);
+  }, []);
+
+  return (
+    <div className="app-layout">
+      {/* Mobile overlay */}
+      {sidebarOpen && (
+        <div
+          className="modal-overlay"
+          style={{ zIndex: 25 }}
+          onClick={() => setSidebarOpen(false)}
+        />
+      )}
+
+      <Sidebar
+        user={user}
+        lists={lists}
+        setLists={setLists}
+        selectedListId={selectedListId}
+        onListSelect={handleListSelect}
+        mobileOpen={sidebarOpen}
+        onClose={() => setSidebarOpen(false)}
+      />
+
+      <div className="main-content">
+        <TaskList
+          key={`${selectedListId}-${refreshKey}`}
+          user={user}
+          listId={selectedListId}
+          lists={lists}
+          tasks={tasks}
+          setTasks={setTasks}
+          selectedTaskId={selectedTask?.id ?? null}
+          onTaskSelect={handleTaskSelect}
+          showCompleted={showCompleted}
+          onToggleCompleted={() => setShowCompleted((p) => !p)}
+          onMenuOpen={() => setSidebarOpen(true)}
+          onRefresh={refresh}
+        />
+      </div>
+
+      {selectedTask && (
+        <TaskDetail
+          task={selectedTask}
+          onClose={() => setSelectedTask(null)}
+          onUpdate={handleTaskUpdate}
+          onDelete={() => { setSelectedTask(null); refresh(); }}
+          listId={selectedTask.listId}
+        />
+      )}
+
+      {/* Mobile FAB */}
+      <button
+        className="fab"
+        id="mobile-add-task"
+        aria-label="Add task"
+        onClick={() => {
+          // trigger add task from task list — use custom event
+          document.dispatchEvent(new CustomEvent("checkflow:addTask"));
+        }}
+      >
+        <svg width="22" height="22" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2.5">
+          <line x1="12" y1="5" x2="12" y2="19" /><line x1="5" y1="12" x2="19" y2="12" />
+        </svg>
+      </button>
+    </div>
+  );
+}

src/components/layout/Sidebar.tsx

@@ -0,0 +1,246 @@
+"use client";
+import { useState, useEffect, useRef } from "react";
+import { signOut } from "next-auth/react";
+
+interface User { id: string; name?: string | null; email?: string | null }
+interface List { id: string; name: string; color: string; icon: string; _count?: { tasks: number } }
+
+const LIST_COLORS = ["#4B7BF5","#EF4444","#10B981","#F59E0B","#8B5CF6","#EC4899","#06B6D4","#F97316","#6366F1","#14B8A6"];
+const LIST_ICONS: Record<string, string> = { list:"≡", inbox:"⌂", star:"★", work:"💼", personal:"👤", shopping:"🛒", health:"❤️", study:"📚" };
+
+interface SidebarProps {
+  user: User; lists: List[]; setLists: (l: List[]) => void;
+  selectedListId: string | null; onListSelect: (id: string) => void;
+  mobileOpen: boolean; onClose: () => void;
+}
+
+export function Sidebar({ user, lists, setLists, selectedListId, onListSelect, mobileOpen, onClose }: SidebarProps) {
+  const [showNewList, setShowNewList] = useState(false);
+  const [newListName, setNewListName] = useState("");
+  const [newListColor, setNewListColor] = useState(LIST_COLORS[0]);
+  const [editList, setEditList] = useState<List | null>(null);
+  const [userMenuOpen, setUserMenuOpen] = useState(false);
+  const [showImport, setShowImport] = useState(false);
+  const [importListId, setImportListId] = useState("");
+  const [importing, setImporting] = useState(false);
+  const [importResult, setImportResult] = useState("");
+  const [theme, setTheme] = useState("light");
+  const inputRef = useRef<HTMLInputElement>(null);
+  const fileRef = useRef<HTMLInputElement>(null);
+
+  useEffect(() => {
+    const t = localStorage.getItem("theme") || "light";
+    setTheme(t);
+  }, []);
+
+  useEffect(() => {
+    fetch("/api/lists")
+      .then((r) => r.json())
+      .then((data) => {
+        if (Array.isArray(data)) {
+          setLists(data);
+          if (!selectedListId && data.length > 0) onListSelect(data[0].id);
+        }
+      });
+  }, []);
+
+  useEffect(() => {
+    if (showNewList) setTimeout(() => inputRef.current?.focus(), 50);
+  }, [showNewList]);
+
+  const toggleTheme = () => {
+    const next = theme === "light" ? "dark" : "light";
+    setTheme(next);
+    localStorage.setItem("theme", next);
+    document.documentElement.setAttribute("data-theme", next);
+  };
+
+  const createList = async () => {
+    const name = newListName.trim();
+    if (!name) return;
+    const res = await fetch("/api/lists", {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({ name, color: newListColor }),
+    });
+    if (res.ok) {
+      const list = await res.json();
+      setLists([...lists, list]);
+      setNewListName("");
+      setShowNewList(false);
+      onListSelect(list.id);
+    }
+  };
+
+  const deleteList = async (id: string) => {
+    if (!confirm("Delete this list and all its tasks?")) return;
+    await fetch(`/api/lists/${id}`, { method: "DELETE" });
+    const updated = lists.filter((l) => l.id !== id);
+    setLists(updated);
+    if (selectedListId === id) onListSelect(updated[0]?.id || "");
+  };
+
+  const handleImport = async () => {
+    const file = fileRef.current?.files?.[0];
+    if (!file || !importListId) return;
+    setImporting(true);
+    try {
+      const formData = new FormData();
+      formData.append("file", file);
+      formData.append("listId", importListId);
+      const res = await fetch("/api/import", { method: "POST", body: formData });
+      const data = await res.json().catch(() => ({}));
+      if (res.ok) {
+        setImportResult(`✓ Imported ${data.imported} tasks`);
+        // Reset file input
+        if (fileRef.current) fileRef.current.value = "";
+        // Refresh list counts
+        const listsRes = await fetch("/api/lists");
+        if (listsRes.ok) { const updated = await listsRes.json(); if (Array.isArray(updated)) setLists(updated); }
+        setTimeout(() => { setShowImport(false); setImportResult(""); }, 2000);
+      } else {
+        setImportResult(`Error: ${data.error || "Import failed"}`);
+      }
+    } catch (err) {
+      console.error("[Sidebar] import failed", err);
+      setImportResult("Error: Network error");
+    } finally {
+      setImporting(false);
+    }
+  };
+
+  const initials = user.name?.split(" ").map((n) => n[0]).join("").toUpperCase().slice(0, 2) || "?";
+
+  return (
+    <aside className={`sidebar${mobileOpen ? " mobile-open" : ""}`}>
+      {/* Header */}
+      <div className="sidebar-header">
+        <div className="sidebar-logo">✓</div>
+        <span className="sidebar-title">CheckFlow</span>
+        <button className="icon-btn" id="theme-toggle" onClick={toggleTheme} title="Toggle theme" style={{ marginLeft: "auto" }}>
+          {theme === "light" ? (
+            <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2"><circle cx="12" cy="12" r="5"/><line x1="12" y1="1" x2="12" y2="3"/><line x1="12" y1="21" x2="12" y2="23"/><line x1="4.22" y1="4.22" x2="5.64" y2="5.64"/><line x1="18.36" y1="18.36" x2="19.78" y2="19.78"/><line x1="1" y1="12" x2="3" y2="12"/><line x1="21" y1="12" x2="23" y2="12"/><line x1="4.22" y1="19.78" x2="5.64" y2="18.36"/><line x1="18.36" y1="5.64" x2="19.78" y2="4.22"/></svg>
+          ) : (
+            <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2"><path d="M21 12.79A9 9 0 1 1 11.21 3 7 7 0 0 0 21 12.79z"/></svg>
+          )}
+        </button>
+      </div>
+
+      {/* Nav */}
+      <nav className="sidebar-nav">
+        <div className="sidebar-section">
+          <div className="sidebar-section-label">Lists</div>
+          {lists.map((list) => (
+            <div
+              key={list.id}
+              className={`sidebar-item${selectedListId === list.id ? " active" : ""}`}
+              onClick={() => onListSelect(list.id)}
+              id={`list-item-${list.id}`}
+            >
+              <div className="list-dot" style={{ background: list.color }} />
+              <span className="item-label">{list.name}</span>
+              <span className="item-count">{list._count?.tasks || ""}</span>
+              <button
+                className="icon-btn"
+                style={{ width: 22, height: 22, opacity: 0.5 }}
+                onClick={(e) => { e.stopPropagation(); deleteList(list.id); }}
+                title="Delete list"
+              >
+                <svg width="12" height="12" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2"><polyline points="3 6 5 6 21 6"/><path d="M19 6l-1 14H6L5 6"/><path d="M10 11v6M14 11v6"/><path d="M9 6V4h6v2"/></svg>
+              </button>
+            </div>
+          ))}
+        </div>
+
+        {/* New list */}
+        {showNewList ? (
+          <div style={{ padding: "4px 8px" }}>
+            <div style={{ display: "flex", flexWrap: "wrap", gap: 6, padding: "6px 4px 8px" }}>
+              {LIST_COLORS.map((c) => (
+                <div
+                  key={c}
+                  className={`color-swatch${newListColor === c ? " selected" : ""}`}
+                  style={{ background: c, color: c }}
+                  onClick={() => setNewListColor(c)}
+                />
+              ))}
+            </div>
+            <input
+              ref={inputRef}
+              className="form-input"
+              placeholder="List name"
+              value={newListName}
+              onChange={(e) => setNewListName(e.target.value)}
+              onKeyDown={(e) => { if (e.key === "Enter") createList(); if (e.key === "Escape") setShowNewList(false); }}
+              style={{ marginBottom: 6 }}
+            />
+            <div style={{ display: "flex", gap: 6 }}>
+              <button className="btn btn-primary btn-sm" style={{ flex: 1 }} onClick={createList}>Create</button>
+              <button className="btn btn-ghost btn-sm" onClick={() => setShowNewList(false)}>Cancel</button>
+            </div>
+          </div>
+        ) : (
+          <button id="new-list-btn" className="sidebar-add-btn" onClick={() => setShowNewList(true)}>
+            <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2.5"><line x1="12" y1="5" x2="12" y2="19"/><line x1="5" y1="12" x2="19" y2="12"/></svg>
+            New List
+          </button>
+        )}
+
+        <div className="sidebar-section" style={{ borderTop: "1px solid var(--border)", paddingTop: 12, marginTop: 4 }}>
+          <button id="import-btn" className="sidebar-add-btn" onClick={() => { setShowImport(true); setImportListId(lists[0]?.id || ""); }}>
+            <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2"><path d="M21 15v4a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2v-4"/><polyline points="17 8 12 3 7 8"/><line x1="12" y1="3" x2="12" y2="15"/></svg>
+            Import Tasks
+          </button>
+        </div>
+      </nav>
+
+      {/* User footer */}
+      <div className="sidebar-footer">
+        <div className="user-card" id="user-menu-btn" onClick={() => setUserMenuOpen((p) => !p)} style={{ position: "relative" }}>
+          <div className="user-avatar" style={{ background: "#4B7BF5" }}>{initials}</div>
+          <div className="user-info">
+            <div className="user-name">{user.name}</div>
+            <div className="user-email">{user.email}</div>
+          </div>
+          {userMenuOpen && (
+            <div className="dropdown" style={{ bottom: "100%", left: 0, right: 0, marginBottom: 4 }}>
+              <div className="dropdown-item danger" id="signout-btn" onClick={() => signOut({ callbackUrl: "/login" })}>
+                <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2"><path d="M9 21H5a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2h4"/><polyline points="16 17 21 12 16 7"/><line x1="21" y1="12" x2="9" y2="12"/></svg>
+                Sign out
+              </div>
+            </div>
+          )}
+        </div>
+      </div>
+
+      {/* Import modal */}
+      {showImport && (
+        <div className="modal-overlay" onClick={() => setShowImport(false)}>
+          <div className="modal" onClick={(e) => e.stopPropagation()}>
+            <h2 className="modal-title">Import Tasks</h2>
+            <div className="form-group">
+              <label className="form-label">Target List</label>
+              <select className="form-input" value={importListId} onChange={(e) => setImportListId(e.target.value)}>
+                {lists.map((l) => <option key={l.id} value={l.id}>{l.name}</option>)}
+              </select>
+            </div>
+            <div className="form-group">
+              <label className="form-label">File (CSV or ICS from TickTick)</label>
+              <input ref={fileRef} type="file" accept=".csv,.ics" className="form-input" />
+            </div>
+            <p style={{ fontSize: 12, color: "var(--text-tertiary)", marginBottom: 12 }}>
+              TickTick: Settings → Export → Export as CSV or iCalendar
+            </p>
+            {importResult && <p style={{ fontSize: 13, color: importResult.startsWith("✓") ? "var(--success)" : "var(--danger)", marginBottom: 12 }}>{importResult}</p>}
+            <div className="modal-footer">
+              <button className="btn btn-ghost" onClick={() => setShowImport(false)}>Cancel</button>
+              <button id="import-submit-btn" className="btn btn-primary" onClick={handleImport} disabled={importing}>
+                {importing ? "Importing..." : "Import"}
+              </button>
+            </div>
+          </div>
+        </div>
+      )}
+    </aside>
+  );
+}

src/components/tasks/TaskDetail.tsx

@@ -0,0 +1,372 @@
+"use client";
+import { useState, useEffect, useCallback, useRef } from "react";
+
+interface Task {
+  id: string; listId: string; parentId: string | null; title: string; note: string | null;
+  completed: boolean; completedAt: string | null; dueDate: string | null; priority: number;
+  sortOrder: number; createdAt: string; updatedAt: string;
+  children: Task[]; tags: { tag: { id: string; name: string; color: string } }[];
+}
+
+const PRIORITY_MAP = [
+  { label: "None", color: "var(--text-tertiary)", icon: "" },
+  { label: "Low", color: "var(--priority-low)", icon: "▼" },
+  { label: "Medium", color: "var(--priority-medium)", icon: "▶" },
+  { label: "High", color: "var(--priority-high)", icon: "▲" },
+];
+
+interface Props {
+  task: Task; listId: string;
+  onClose: () => void;
+  onUpdate: (t: Task) => void;
+  onDelete: () => void;
+}
+
+export function TaskDetail({ task, listId, onClose, onUpdate, onDelete }: Props) {
+  const [title, setTitle] = useState(task.title);
+  const [note, setNote] = useState(task.note || "");
+  const [dueDate, setDueDate] = useState(task.dueDate ? task.dueDate.split("T")[0] : "");
+  const [priority, setPriority] = useState(task.priority);
+  const [newSubtitle, setNewSubtitle] = useState("");
+  const [subtasks, setSubtasks] = useState(task.children || []);
+  const [saving, setSaving] = useState(false);
+
+  // Store timer + current task id in refs to prevent stale saves across task switches
+  const saveTimer = useRef<ReturnType<typeof setTimeout> | null>(null);
+  const currentTaskId = useRef(task.id);
+  const noteRef = useRef<HTMLTextAreaElement>(null);
+
+  // Sync state when switching to a different task — clear any pending timer first
+  useEffect(() => {
+    if (saveTimer.current) {
+      clearTimeout(saveTimer.current);
+      saveTimer.current = null;
+    }
+    currentTaskId.current = task.id;
+    setTitle(task.title);
+    setNote(task.note || "");
+    setDueDate(task.dueDate ? task.dueDate.split("T")[0] : "");
+    setPriority(task.priority);
+    setSubtasks(task.children || []);
+  }, [task.id]);
+
+  // Cleanup timer on unmount
+  useEffect(() => {
+    return () => {
+      if (saveTimer.current) clearTimeout(saveTimer.current);
+    };
+  }, []);
+
+  const save = useCallback(async (taskId: string, data: Record<string, unknown>) => {
+    // Guard: don't save if task has changed since debounce was scheduled
+    if (taskId !== currentTaskId.current) return;
+    setSaving(true);
+    try {
+      const res = await fetch(`/api/tasks/${taskId}`, {
+        method: "PATCH",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify(data),
+      });
+      if (res.ok) {
+        const updated = await res.json();
+        // Only update if we're still on the same task
+        if (taskId === currentTaskId.current) {
+          onUpdate({ ...updated, children: subtasks });
+        }
+      }
+    } catch (err) {
+      console.error("[TaskDetail] save failed", err);
+    } finally {
+      if (taskId === currentTaskId.current) setSaving(false);
+    }
+  }, [onUpdate, subtasks]);
+
+  const debounceSave = useCallback((overrides: Record<string, unknown>) => {
+    if (saveTimer.current) clearTimeout(saveTimer.current);
+    const taskId = currentTaskId.current;
+    saveTimer.current = setTimeout(() => save(taskId, overrides), 800);
+  }, [save]);
+
+  // Insert text at cursor position in the note textarea
+  const insertAtCursor = useCallback((before: string, after = "", placeholder = "") => {
+    const ta = noteRef.current;
+    if (!ta) {
+      setNote((n) => { const v = n + before + placeholder + after; debounceSave({ note: v }); return v; });
+      return;
+    }
+    const start = ta.selectionStart ?? ta.value.length;
+    const end = ta.selectionEnd ?? ta.value.length;
+    const selected = ta.value.slice(start, end) || placeholder;
+    const newVal = ta.value.slice(0, start) + before + selected + after + ta.value.slice(end);
+    setNote(newVal);
+    debounceSave({ note: newVal });
+    // Restore cursor after React re-render
+    requestAnimationFrame(() => {
+      ta.focus();
+      ta.selectionStart = start + before.length;
+      ta.selectionEnd = start + before.length + selected.length;
+    });
+  }, [debounceSave]);
+
+  const handleToggleCompleted = useCallback(async (newCompleted: boolean) => {
+    try {
+      const res = await fetch(`/api/tasks/${task.id}`, {
+        method: "PATCH",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ completed: newCompleted }),
+      });
+      if (res.ok) {
+        const updated = await res.json();
+        onUpdate({ ...updated, children: subtasks });
+      }
+    } catch (err) {
+      console.error("[TaskDetail] toggle failed", err);
+    }
+  }, [task.id, subtasks, onUpdate]);
+
+  const handleDelete = useCallback(async () => {
+    if (!confirm("Delete this task?")) return;
+    try {
+      await fetch(`/api/tasks/${task.id}`, { method: "DELETE" });
+      onDelete();
+    } catch (err) {
+      console.error("[TaskDetail] delete failed", err);
+    }
+  }, [task.id, onDelete]);
+
+  const addSubtask = useCallback(async () => {
+    const t = newSubtitle.trim();
+    if (!t) return;
+    try {
+      const res = await fetch("/api/tasks", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ title: t, listId, parentId: task.id }),
+      });
+      if (res.ok) {
+        const sub = await res.json();
+        setSubtasks((prev) => {
+          const next = [...prev, sub];
+          onUpdate({ ...task, children: next });
+          return next;
+        });
+        setNewSubtitle("");
+      }
+    } catch (err) {
+      console.error("[TaskDetail] addSubtask failed", err);
+    }
+  }, [newSubtitle, listId, task, onUpdate]);
+
+  const toggleSubtask = useCallback(async (sub: Task) => {
+    try {
+      const res = await fetch(`/api/tasks/${sub.id}`, {
+        method: "PATCH",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ completed: !sub.completed }),
+      });
+      if (res.ok) {
+        const updated = await res.json();
+        setSubtasks((prev) => {
+          const next = prev.map((s) => (s.id === sub.id ? updated : s));
+          onUpdate({ ...task, children: next });
+          return next;
+        });
+      }
+    } catch (err) {
+      console.error("[TaskDetail] toggleSubtask failed", err);
+    }
+  }, [task, onUpdate]);
+
+  const deleteSubtask = useCallback(async (id: string) => {
+    try {
+      await fetch(`/api/tasks/${id}`, { method: "DELETE" });
+      setSubtasks((prev) => {
+        const next = prev.filter((s) => s.id !== id);
+        onUpdate({ ...task, children: next });
+        return next;
+      });
+    } catch (err) {
+      console.error("[TaskDetail] deleteSubtask failed", err);
+    }
+  }, [task, onUpdate]);
+
+  const completedCount = subtasks.filter((s) => s.completed).length;
+  const progressPct = subtasks.length > 0 ? Math.round((completedCount / subtasks.length) * 100) : 0;
+
+  return (
+    <aside className="detail-panel">
+      {/* Header */}
+      <div className="detail-header">
+        <button
+          className={`task-check-btn${task.completed ? " checked" : ""}`}
+          style={{ width: 22, height: 22 }}
+          onClick={() => handleToggleCompleted(!task.completed)}
+          aria-label={task.completed ? "Mark incomplete" : "Mark complete"}
+        />
+        <span style={{ flex: 1, fontSize: 12, color: "var(--text-tertiary)", fontWeight: 500 }}>
+          {saving ? "Saving…" : "Auto-saved"}
+        </span>
+        <button className="btn btn-ghost btn-sm btn-danger" id="delete-task-btn" onClick={handleDelete} title="Delete task">
+          <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2"><polyline points="3 6 5 6 21 6"/><path d="M19 6l-1 14H6L5 6"/><path d="M10 11v6M14 11v6"/><path d="M9 6V4h6v2"/></svg>
+        </button>
+        <button className="detail-close-btn" id="detail-close-btn" onClick={onClose} title="Close">
+          <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2"><line x1="18" y1="6" x2="6" y2="18"/><line x1="6" y1="6" x2="18" y2="18"/></svg>
+        </button>
+      </div>
+
+      {/* Body */}
+      <div className="detail-body">
+        {/* Title */}
+        <textarea
+          id="detail-title"
+          className="detail-title-input"
+          value={title}
+          onChange={(e) => {
+            setTitle(e.target.value);
+            debounceSave({ title: e.target.value });
+          }}
+          placeholder="Task title"
+          rows={2}
+          style={{
+            textDecoration: task.completed ? "line-through" : "none",
+            color: task.completed ? "var(--text-tertiary)" : "var(--text-primary)",
+          }}
+        />
+
+        {/* Priority */}
+        <div className="detail-section">
+          <div className="detail-section-label">Priority</div>
+          <div className="priority-selector">
+            {PRIORITY_MAP.map((p, i) => (
+              <button
+                key={i}
+                id={`priority-${i}`}
+                className={`priority-btn${priority === i ? ` active-${p.label.toLowerCase()}` : ""}`}
+                style={{ color: priority === i ? p.color : undefined }}
+                onClick={() => { setPriority(i); debounceSave({ priority: i }); }}
+              >
+                {p.icon && <span style={{ color: p.color }}>{p.icon}</span>}
+                {p.label}
+              </button>
+            ))}
+          </div>
+        </div>
+
+        {/* Due date */}
+        <div className="detail-section">
+          <div className="detail-section-label">Due Date</div>
+          <div style={{ display: "flex", gap: 8, alignItems: "center" }}>
+            <input
+              id="due-date-input"
+              type="date"
+              className="form-input"
+              value={dueDate}
+              onChange={(e) => {
+                setDueDate(e.target.value);
+                debounceSave({ dueDate: e.target.value || null });
+              }}
+              style={{ width: "auto" }}
+            />
+            {dueDate && (
+              <button
+                className="btn btn-ghost btn-sm"
+                onClick={() => { setDueDate(""); debounceSave({ dueDate: null }); }}
+              >
+                Clear
+              </button>
+            )}
+          </div>
+        </div>
+
+        {/* Note / Memo */}
+        <div className="detail-section" style={{ flex: 1 }}>
+          <div className="detail-section-label">Notes</div>
+          <div className="note-editor-wrap">
+            <div className="note-editor-toolbar">
+              <button className="note-toolbar-btn" title="Bold (Ctrl+B)" onClick={() => insertAtCursor("**", "**", "bold")}>B</button>
+              <button className="note-toolbar-btn" title="Italic (Ctrl+I)" style={{ fontStyle: "italic" }} onClick={() => insertAtCursor("*", "*", "italic")}>I</button>
+              <button className="note-toolbar-btn" title="Heading" onClick={() => insertAtCursor("## ", "", "Heading")}>H</button>
+              <button className="note-toolbar-btn" title="Bullet list" onClick={() => insertAtCursor("\n- ", "", "item")}>•</button>
+              <button className="note-toolbar-btn" title="Numbered list" onClick={() => insertAtCursor("\n1. ", "", "item")}>1.</button>
+              <button className="note-toolbar-btn" title="Checkbox" onClick={() => insertAtCursor("\n- [ ] ", "", "task")}>☐</button>
+              <button className="note-toolbar-btn" title="Code" style={{ fontFamily: "monospace", fontSize: 11 }} onClick={() => insertAtCursor("`", "`", "code")}>{"`"}</button>
+            </div>
+            <textarea
+              ref={noteRef}
+              id="note-textarea"
+              className="note-textarea"
+              placeholder={"Add notes, details, or anything you need to remember…\n\nMarkdown: **bold**, *italic*, # heading, - list, - [ ] checkbox"}
+              value={note}
+              onChange={(e) => {
+                setNote(e.target.value);
+                debounceSave({ note: e.target.value });
+              }}
+            />
+          </div>
+        </div>
+
+        {/* Sub-tasks */}
+        <div className="detail-section">
+          <div style={{ display: "flex", alignItems: "center", justifyContent: "space-between", marginBottom: 8 }}>
+            <div className="detail-section-label">Sub-tasks</div>
+            {subtasks.length > 0 && (
+              <span style={{ fontSize: 11, color: "var(--text-tertiary)" }}>{completedCount}/{subtasks.length}</span>
+            )}
+          </div>
+
+          {subtasks.length > 0 && (
+            <div className="progress-bar" style={{ marginBottom: 10 }}>
+              <div className="progress-bar-fill" style={{ width: `${progressPct}%` }} />
+            </div>
+          )}
+
+          <div className="detail-subtasks">
+            {subtasks.map((sub) => (
+              <div
+                key={sub.id}
+                className={`detail-subtask-row${sub.completed ? " completed" : ""}`}
+                id={`detail-sub-${sub.id}`}
+              >
+                <button
+                  className={`subtask-check-btn${sub.completed ? " checked" : ""}`}
+                  onClick={() => toggleSubtask(sub)}
+                  aria-label="Toggle subtask"
+                />
+                <span className="detail-subtask-title">{sub.title}</span>
+                <button
+                  className="icon-btn"
+                  style={{ width: 20, height: 20, opacity: 0.4 }}
+                  onClick={() => deleteSubtask(sub.id)}
+                  aria-label="Delete subtask"
+                >
+                  <svg width="10" height="10" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2"><line x1="18" y1="6" x2="6" y2="18"/><line x1="6" y1="6" x2="18" y2="18"/></svg>
+                </button>
+              </div>
+            ))}
+            <div className="add-subtask-row">
+              <span style={{ fontSize: 16, lineHeight: 1, color: "var(--accent)" }}>+</span>
+              <input
+                id="add-subtask-input"
+                placeholder="Add sub-task…"
+                style={{ flex: 1, background: "none", fontSize: 13, color: "var(--text-primary)" }}
+                value={newSubtitle}
+                onChange={(e) => setNewSubtitle(e.target.value)}
+                onKeyDown={(e) => {
+                  if (e.key === "Enter") { e.preventDefault(); addSubtask(); }
+                }}
+              />
+              {newSubtitle.trim() && (
+                <button className="btn btn-primary btn-sm" id="add-subtask-btn" onClick={addSubtask}>Add</button>
+              )}
+            </div>
+          </div>
+        </div>
+
+        {/* Metadata */}
+        <div style={{ fontSize: 11, color: "var(--text-tertiary)", paddingTop: 8, borderTop: "1px solid var(--border)" }}>
+          Created {new Date(task.createdAt).toLocaleDateString("ko-KR", { year: "numeric", month: "short", day: "numeric" })}
+        </div>
+      </div>
+    </aside>
+  );
+}

src/components/tasks/TaskList.tsx

@@ -0,0 +1,269 @@
+"use client";
+import { useState, useEffect, useRef, useCallback } from "react";
+
+interface Task {
+  id: string; listId: string; parentId: string | null; title: string; note: string | null;
+  completed: boolean; completedAt: string | null; dueDate: string | null; priority: number;
+  sortOrder: number; createdAt: string; updatedAt: string;
+  children: Task[]; tags: { tag: { id: string; name: string; color: string } }[];
+}
+interface List { id: string; name: string; color: string; icon: string }
+interface User { id: string; name?: string | null; email?: string | null }
+
+const PRIORITY_COLORS = ["transparent", "var(--priority-low)", "var(--priority-medium)", "var(--priority-high)"];
+const PRIORITY_LABELS = ["", "Low", "Medium", "High"];
+
+function formatDate(d: string | null) {
+  if (!d) return null;
+  const date = new Date(d);
+  const now = new Date();
+  const isToday = date.toDateString() === now.toDateString();
+  const isTomorrow = date.toDateString() === new Date(now.getTime() + 86400000).toDateString();
+  if (isToday) return "Today";
+  if (isTomorrow) return "Tomorrow";
+  return date.toLocaleDateString("en-US", { month: "short", day: "numeric" });
+}
+
+function isOverdue(d: string | null) {
+  if (!d) return false;
+  return new Date(d) < new Date() && new Date(d).toDateString() !== new Date().toDateString();
+}
+
+interface TaskItemProps {
+  task: Task; isSelected: boolean;
+  onSelect: (t: Task) => void;
+  onToggle: (id: string, completed: boolean) => void;
+}
+
+function TaskItem({ task, isSelected, onSelect, onToggle }: TaskItemProps) {
+  const [expanded, setExpanded] = useState(false);
+  const completedChildren = task.children.filter((c) => c.completed).length;
+
+  return (
+    <div>
+      <div
+        className={`task-item${task.completed ? " completed" : ""}${isSelected ? " selected" : ""}`}
+        onClick={() => onSelect(task)}
+        id={`task-${task.id}`}
+      >
+        <button
+          className={`task-check-btn${task.completed ? " checked" : ""}`}
+          onClick={(e) => { e.stopPropagation(); onToggle(task.id, !task.completed); }}
+          aria-label={task.completed ? "Mark incomplete" : "Mark complete"}
+        />
+        <div className="task-body">
+          <div className="task-title">{task.title}</div>
+          <div className="task-meta">
+            {task.priority > 0 && (
+              <div className="task-priority-dot" style={{ background: PRIORITY_COLORS[task.priority] }} title={PRIORITY_LABELS[task.priority]} />
+            )}
+            {task.dueDate && (
+              <span className={`task-due${isOverdue(task.dueDate) && !task.completed ? " overdue" : ""}`}>
+                <svg width="10" height="10" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2"><rect x="3" y="4" width="18" height="18" rx="2"/><line x1="16" y1="2" x2="16" y2="6"/><line x1="8" y1="2" x2="8" y2="6"/><line x1="3" y1="10" x2="21" y2="10"/></svg>
+                {formatDate(task.dueDate)}
+              </span>
+            )}
+            {task.children.length > 0 && (
+              <span
+                className="task-sub-count"
+                onClick={(e) => { e.stopPropagation(); setExpanded((p) => !p); }}
+              >
+                <svg width="10" height="10" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2"><polyline points="9 18 15 12 9 6"/></svg>
+                {completedChildren}/{task.children.length}
+              </span>
+            )}
+          </div>
+          {task.note && !task.completed && (
+            <div className="task-note-preview">{task.note.replace(/[#*`]/g, "").slice(0, 80)}</div>
+          )}
+        </div>
+      </div>
+
+      {/* Sub-tasks */}
+      {task.children.length > 0 && expanded && (
+        <div className="subtask-list">
+          {task.children.map((child) => (
+            <div
+              key={child.id}
+              className={`subtask-item${child.completed ? " completed" : ""}`}
+              onClick={() => onSelect(child)}
+              id={`subtask-${child.id}`}
+            >
+              <button
+                className={`subtask-check-btn${child.completed ? " checked" : ""}`}
+                onClick={(e) => { e.stopPropagation(); onToggle(child.id, !child.completed); }}
+                aria-label={child.completed ? "Mark incomplete" : "Mark complete"}
+              />
+              <span className="subtask-title">{child.title}</span>
+            </div>
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}
+
+interface Props {
+  user: User; listId: string | null; lists: List[]; tasks: Task[];
+  setTasks: React.Dispatch<React.SetStateAction<Task[]>>;
+  selectedTaskId: string | null; onTaskSelect: (t: Task | null) => void;
+  showCompleted: boolean; onToggleCompleted: () => void;
+  onMenuOpen: () => void; onRefresh: () => void;
+}
+
+export function TaskList({ user, listId, lists, tasks, setTasks, selectedTaskId, onTaskSelect, showCompleted, onToggleCompleted, onMenuOpen, onRefresh }: Props) {
+  const [newTaskTitle, setNewTaskTitle] = useState("");
+  const [loading, setLoading] = useState(false);
+  const inputRef = useRef<HTMLInputElement>(null);
+  const currentList = lists.find((l) => l.id === listId);
+
+  const fetchTasks = useCallback(async () => {
+    if (!listId) return;
+    setLoading(true);
+    try {
+      const res = await fetch(`/api/tasks?listId=${listId}&showCompleted=${showCompleted}`);
+      if (!res.ok) throw new Error(`HTTP ${res.status}`);
+      const data = await res.json();
+      setTasks(Array.isArray(data) ? data : []);
+    } catch (err) {
+      console.error("[TaskList] fetchTasks failed", err);
+    } finally {
+      setLoading(false);
+    }
+  }, [listId, showCompleted]);
+
+  useEffect(() => { fetchTasks(); }, [fetchTasks]);
+
+  useEffect(() => {
+    const handler = () => inputRef.current?.focus();
+    document.addEventListener("checkflow:addTask", handler);
+    return () => document.removeEventListener("checkflow:addTask", handler);
+  }, []);
+
+  const handleToggle = useCallback(async (id: string, completed: boolean) => {
+    try {
+      const res = await fetch(`/api/tasks/${id}`, {
+        method: "PATCH",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ completed }),
+      });
+      if (!res.ok) throw new Error(`HTTP ${res.status}`);
+      const updated = await res.json();
+      // Functional update avoids stale closure on `tasks`
+      setTasks((prev) =>
+        prev.map((t) => {
+          if (t.id === id) return { ...t, completed, completedAt: updated.completedAt };
+          return { ...t, children: t.children.map((c) => (c.id === id ? { ...c, completed } : c)) };
+        }).filter((t) => showCompleted || !t.completed)
+      );
+      onRefresh();
+    } catch (err) {
+      console.error("[TaskList] handleToggle failed", err);
+    }
+  }, [showCompleted, onRefresh]);
+
+  const handleAddTask = async (e: React.FormEvent) => {
+    e.preventDefault();
+    const title = newTaskTitle.trim();
+    if (!title || !listId) return;
+    try {
+      const res = await fetch("/api/tasks", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ title, listId }),
+      });
+      if (!res.ok) throw new Error(`HTTP ${res.status}`);
+      const task = await res.json();
+      setTasks((prev) => [...prev, task]);
+      setNewTaskTitle("");
+      onRefresh();
+    } catch (err) {
+      console.error("[TaskList] handleAddTask failed", err);
+    }
+  };
+
+  if (!listId) {
+    return (
+      <div style={{ display: "flex", flexDirection: "column", alignItems: "center", justifyContent: "center", height: "100%", color: "var(--text-tertiary)" }}>
+        <svg width="48" height="48" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="1.5" style={{ opacity: 0.3, marginBottom: 12 }}><path d="M9 11l3 3L22 4"/><path d="M21 12v7a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2h11"/></svg>
+        <p>Select a list to get started</p>
+      </div>
+    );
+  }
+
+  const incompleteTasks = tasks.filter((t) => !t.completed);
+  const completedTasks = tasks.filter((t) => t.completed);
+
+  return (
+    <div style={{ display: "flex", flexDirection: "column", height: "100%" }}>
+      {/* Header */}
+      <div className="main-header">
+        <button className="icon-btn mobile-only" id="menu-btn" onClick={onMenuOpen} aria-label="Menu">
+          <svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2"><line x1="3" y1="6" x2="21" y2="6"/><line x1="3" y1="12" x2="21" y2="12"/><line x1="3" y1="18" x2="21" y2="18"/></svg>
+        </button>
+        <div className="main-header-title" style={{ color: currentList?.color }}>
+          {currentList?.name || "Tasks"}
+        </div>
+        <div className="main-header-actions">
+          <button
+            id="toggle-completed-btn"
+            className="btn btn-ghost btn-sm"
+            onClick={onToggleCompleted}
+            title={showCompleted ? "Hide completed" : "Show completed"}
+          >
+            <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2"><polyline points="20 6 9 17 4 12"/></svg>
+            {showCompleted ? "Hide done" : "Show done"}
+          </button>
+        </div>
+      </div>
+
+      {/* Task list */}
+      <div className="task-list-container">
+        {loading && (
+          <div style={{ padding: "20px", textAlign: "center", color: "var(--text-tertiary)" }}>Loading...</div>
+        )}
+        {!loading && incompleteTasks.length === 0 && completedTasks.length === 0 && (
+          <div className="task-list-empty">
+            <svg width="56" height="56" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="1.5"><path d="M9 11l3 3L22 4"/><path d="M21 12v7a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2h11"/></svg>
+            <p>No tasks yet. Add one below!</p>
+          </div>
+        )}
+        {incompleteTasks.map((task) => (
+          <TaskItem key={task.id} task={task} isSelected={selectedTaskId === task.id} onSelect={onTaskSelect} onToggle={handleToggle} />
+        ))}
+        {showCompleted && completedTasks.length > 0 && (
+          <div>
+            <div style={{ padding: "12px 20px 4px", fontSize: 11, fontWeight: 600, color: "var(--text-tertiary)", textTransform: "uppercase", letterSpacing: "0.5px" }}>
+              Completed ({completedTasks.length})
+            </div>
+            {completedTasks.map((task) => (
+              <TaskItem key={task.id} task={task} isSelected={selectedTaskId === task.id} onSelect={onTaskSelect} onToggle={handleToggle} />
+            ))}
+          </div>
+        )}
+      </div>
+
+      {/* Add task */}
+      <div className="add-task-bar">
+        <button
+          className="task-check-btn"
+          style={{ opacity: 0.4, flexShrink: 0 }}
+          aria-hidden="true"
+        />
+        <form onSubmit={handleAddTask} style={{ flex: 1, display: "flex", gap: 8 }}>
+          <input
+            ref={inputRef}
+            id="add-task-input"
+            className="add-task-input"
+            placeholder="Add a task..."
+            value={newTaskTitle}
+            onChange={(e) => setNewTaskTitle(e.target.value)}
+          />
+          {newTaskTitle.trim() && (
+            <button type="submit" className="btn btn-primary btn-sm" id="add-task-btn">Add</button>
+          )}
+        </form>
+      </div>
+    </div>
+  );
+}

src/lib/auth.ts

@@ -0,0 +1,41 @@
+import { NextAuthOptions } from "next-auth";
+import CredentialsProvider from "next-auth/providers/credentials";
+import { prisma } from "@/lib/prisma";
+import bcrypt from "bcryptjs";
+
+export const authOptions: NextAuthOptions = {
+  session: { strategy: "jwt" },
+  pages: {
+    signIn: "/login",
+    newUser: "/register",
+  },
+  providers: [
+    CredentialsProvider({
+      name: "credentials",
+      credentials: {
+        email: { label: "Email", type: "email" },
+        password: { label: "Password", type: "password" },
+      },
+      async authorize(credentials) {
+        if (!credentials?.email || !credentials?.password) return null;
+        const user = await prisma.user.findUnique({
+          where: { email: credentials.email },
+        });
+        if (!user) return null;
+        const valid = await bcrypt.compare(credentials.password, user.passwordHash);
+        if (!valid) return null;
+        return { id: user.id, email: user.email, name: user.name };
+      },
+    }),
+  ],
+  callbacks: {
+    jwt({ token, user }) {
+      if (user) token.id = user.id;
+      return token;
+    },
+    session({ session, token }) {
+      if (session.user) session.user.id = token.id as string;
+      return session;
+    },
+  },
+};

src/lib/i18n/index.tsx

@@ -0,0 +1,288 @@
+"use client";
+import React, { createContext, useContext, useState, useEffect } from "react";
+
+export type Locale = "en" | "ko" | "ja";
+
+// ============================================================
+//  TRANSLATIONS
+// ============================================================
+const translations = {
+  en: {
+    auth: {
+      welcome: "Welcome back",
+      signIn: "Sign in",
+      signInSub: "Sign in to your account",
+      createAccount: "Create account",
+      createAccountSub: "Start organizing your tasks today",
+      email: "Email",
+      password: "Password",
+      passwordHint: "Min. 8 characters",
+      displayName: "Display Name",
+      namePlaceholder: "Your name",
+      noAccount: "Don't have an account?",
+      hasAccount: "Already have an account?",
+      createOne: "Create one",
+      signInLink: "Sign in",
+      signingIn: "Signing in...",
+      creating: "Creating account...",
+      invalidCredentials: "Invalid email or password.",
+      registrationFailed: "Registration failed.",
+    },
+    sidebar: {
+      lists: "Lists",
+      newList: "New List",
+      create: "Create",
+      cancel: "Cancel",
+      listName: "List name",
+      importTasks: "Import Tasks",
+      signOut: "Sign out",
+      deleteListConfirm: "Delete this list and all its tasks?",
+    },
+    tasks: {
+      addTask: "Add a task...",
+      add: "Add",
+      showDone: "Show done",
+      hideDone: "Hide done",
+      noTasks: "No tasks yet. Add one below!",
+      selectList: "Select a list to get started",
+      completed: "Completed",
+      loading: "Loading...",
+    },
+    detail: {
+      priority: "Priority",
+      dueDate: "Due Date",
+      notes: "Notes",
+      notesPlaceholder: "Add notes, details, or anything you need to remember\u2026\n\nMarkdown: **bold**, *italic*, # heading, - list, - [ ] checkbox",
+      subtasks: "Sub-tasks",
+      addSubtask: "Add sub-task\u2026",
+      autoSaved: "Auto-saved",
+      saving: "Saving\u2026",
+      delete: "Delete task",
+      deleteConfirm: "Delete this task?",
+      close: "Close",
+      clear: "Clear",
+      created: "Created",
+    },
+    priority: { none: "None", low: "Low", medium: "Medium", high: "High" },
+    settings: {
+      theme: "Theme",
+      language: "Language",
+      system: "System",
+      light: "Light",
+      dark: "Dark",
+    },
+    import: {
+      title: "Import Tasks",
+      targetList: "Target List",
+      file: "File (CSV or ICS)",
+      tip: "TickTick: Settings \u2192 Export \u2192 Export as CSV or iCalendar",
+      cancel: "Cancel",
+      import: "Import",
+      importing: "Importing...",
+      error: "Error",
+    },
+    list: { create: "Create list", color: "Color" },
+  },
+
+  ko: {
+    auth: {
+      welcome: "다시 오셨군요",
+      signIn: "로그인",
+      signInSub: "계정에 로그인하세요",
+      createAccount: "계정 만들기",
+      createAccountSub: "오늘부터 할 일을 정리해보세요",
+      email: "이메일",
+      password: "비밀번호",
+      passwordHint: "최소 8자",
+      displayName: "이름",
+      namePlaceholder: "표시될 이름",
+      noAccount: "계정이 없으신가요?",
+      hasAccount: "이미 계정이 있으신가요?",
+      createOne: "만들기",
+      signInLink: "로그인",
+      signingIn: "로그인 중...",
+      creating: "계정 생성 중...",
+      invalidCredentials: "이메일 또는 비밀번호가 올바르지 않습니다.",
+      registrationFailed: "회원가입에 실패했습니다.",
+    },
+    sidebar: {
+      lists: "목록",
+      newList: "새 목록",
+      create: "만들기",
+      cancel: "취소",
+      listName: "목록 이름",
+      importTasks: "가져오기",
+      signOut: "로그아웃",
+      deleteListConfirm: "이 목록과 모든 할 일을 삭제할까요?",
+    },
+    tasks: {
+      addTask: "할 일 추가...",
+      add: "추가",
+      showDone: "완료 표시",
+      hideDone: "완료 숨기기",
+      noTasks: "할 일이 없습니다. 아래에서 추가하세요!",
+      selectList: "목록을 선택하여 시작하세요",
+      completed: "완료됨",
+      loading: "불러오는 중...",
+    },
+    detail: {
+      priority: "우선순위",
+      dueDate: "마감일",
+      notes: "메모",
+      notesPlaceholder: "메모, 세부 정보, 기억해야 할 내용을 추가하세요\u2026\n\nMarkdown: **굵게**, *기울임*, # 제목, - 목록, - [ ] 체크박스",
+      subtasks: "하위 할 일",
+      addSubtask: "하위 항목 추가\u2026",
+      autoSaved: "자동 저장됨",
+      saving: "저장 중\u2026",
+      delete: "삭제",
+      deleteConfirm: "이 할 일을 삭제할까요?",
+      close: "닫기",
+      clear: "초기화",
+      created: "생성일",
+    },
+    priority: { none: "없음", low: "낮음", medium: "보통", high: "높음" },
+    settings: {
+      theme: "테마",
+      language: "언어",
+      system: "시스템",
+      light: "라이트",
+      dark: "다크",
+    },
+    import: {
+      title: "할 일 가져오기",
+      targetList: "대상 목록",
+      file: "파일 (CSV 또는 ICS)",
+      tip: "TickTick: 설정 \u2192 내보내기 \u2192 CSV 또는 iCalendar로 내보내기",
+      cancel: "취소",
+      import: "가져오기",
+      importing: "가져오는 중...",
+      error: "오류",
+    },
+    list: { create: "목록 만들기", color: "색상" },
+  },
+
+  ja: {
+    auth: {
+      welcome: "おかえりなさい",
+      signIn: "サインイン",
+      signInSub: "アカウントにサインイン",
+      createAccount: "アカウント作成",
+      createAccountSub: "今日からタスクを整理しましょう",
+      email: "メールアドレス",
+      password: "パスワード",
+      passwordHint: "8文字以上",
+      displayName: "表示名",
+      namePlaceholder: "あなたの名前",
+      noAccount: "アカウントをお持ちでない方は",
+      hasAccount: "すでにアカウントをお持ちですか?",
+      createOne: "作成する",
+      signInLink: "サインイン",
+      signingIn: "サインイン中...",
+      creating: "アカウント作成中...",
+      invalidCredentials: "メールアドレスまたはパスワードが正しくありません。",
+      registrationFailed: "登録に失敗しました。",
+    },
+    sidebar: {
+      lists: "リスト",
+      newList: "新しいリスト",
+      create: "作成",
+      cancel: "キャンセル",
+      listName: "リスト名",
+      importTasks: "インポート",
+      signOut: "サインアウト",
+      deleteListConfirm: "このリストとすべてのタスクを削除しますか？",
+    },
+    tasks: {
+      addTask: "タスクを追加...",
+      add: "追加",
+      showDone: "完了を表示",
+      hideDone: "完了を非表示",
+      noTasks: "タスクがありません。下から追加してください！",
+      selectList: "リストを選択して始めましょう",
+      completed: "完了済み",
+      loading: "読み込み中...",
+    },
+    detail: {
+      priority: "優先度",
+      dueDate: "期限",
+      notes: "メモ",
+      notesPlaceholder: "メモ、詳細、覚えておくべきことを追加\u2026\n\nMarkdown: **太字**, *斜体*, # 見出し, - リスト, - [ ] チェックボックス",
+      subtasks: "サブタスク",
+      addSubtask: "サブタスクを追加\u2026",
+      autoSaved: "自動保存済み",
+      saving: "保存中\u2026",
+      delete: "削除",
+      deleteConfirm: "このタスクを削除しますか？",
+      close: "閉じる",
+      clear: "クリア",
+      created: "作成日",
+    },
+    priority: { none: "なし", low: "低", medium: "中", high: "高" },
+    settings: {
+      theme: "テーマ",
+      language: "言語",
+      system: "システム",
+      light: "ライト",
+      dark: "ダーク",
+    },
+    import: {
+      title: "タスクをインポート",
+      targetList: "対象リスト",
+      file: "ファイル (CSV または ICS)",
+      tip: "TickTick: 設定 \u2192 エクスポート \u2192 CSVまたはiCalendarでエクスポート",
+      cancel: "キャンセル",
+      import: "インポート",
+      importing: "インポート中...",
+      error: "エラー",
+    },
+    list: { create: "リスト作成", color: "カラー" },
+  },
+} as const;
+
+export type Translations = typeof translations.en;
+export type TranslationKey = keyof Translations;
+
+// ============================================================
+//  CONTEXT
+// ============================================================
+interface I18nContextValue {
+  locale: Locale;
+  setLocale: (l: Locale) => void;
+  t: Translations;
+}
+
+const I18nContext = createContext<I18nContextValue>({
+  locale: "en",
+  setLocale: () => {},
+  t: translations.en,
+});
+
+export function I18nProvider({ children }: { children: React.ReactNode }) {
+  const [locale, setLocaleState] = useState<Locale>("en");
+
+  useEffect(() => {
+    const saved = localStorage.getItem("locale") as Locale | null;
+    if (saved && saved in translations) setLocaleState(saved);
+  }, []);
+
+  const setLocale = (l: Locale) => {
+    setLocaleState(l);
+    localStorage.setItem("locale", l);
+  };
+
+  return (
+    <I18nContext.Provider value={{ locale, setLocale, t: translations[locale] }}>
+      {children}
+    </I18nContext.Provider>
+  );
+}
+
+export function useI18n() {
+  return useContext(I18nContext);
+}
+
+export const LOCALES: { value: Locale; label: string; flag: string }[] = [
+  { value: "en", label: "English", flag: "🇺🇸" },
+  { value: "ko", label: "한국어", flag: "🇰🇷" },
+  { value: "ja", label: "日本語", flag: "🇯🇵" },
+];

src/lib/prisma.ts

@@ -0,0 +1,13 @@
+import { PrismaClient } from "@prisma/client";
+
+const globalForPrisma = globalThis as unknown as {
+  prisma: PrismaClient | undefined;
+};
+
+export const prisma =
+  globalForPrisma.prisma ??
+  new PrismaClient({
+    log: process.env.NODE_ENV === "development" ? ["error", "warn"] : ["error"],
+  });
+
+if (process.env.NODE_ENV !== "production") globalForPrisma.prisma = prisma;

src/proxy.ts

@@ -0,0 +1,24 @@
+import type { NextRequest } from "next/server";
+import { NextResponse } from "next/server";
+import { getToken } from "next-auth/jwt";
+
+export async function proxy(request: NextRequest) {
+  const { pathname } = request.nextUrl;
+
+  // Public paths
+  // /api/dav: DAVx⁵ uses Basic Auth (not session cookie), so it must bypass the JWT check
+  const publicPaths = ["/login", "/register", "/api/auth", "/api/dav", "/icons", "/manifest.json", "/sw.js", "/_next", "/favicon.ico"];
+  const isPublic = publicPaths.some((p) => pathname.startsWith(p));
+  if (isPublic) return NextResponse.next();
+
+  const token = await getToken({ req: request });
+  if (!token) {
+    const loginUrl = new URL("/login", request.url);
+    return NextResponse.redirect(loginUrl);
+  }
+  return NextResponse.next();
+}
+
+export const config = {
+  matcher: ["/((?!_next/static|_next/image|favicon.ico).*)"],
+};

src/types/next-auth.d.ts

@@ -0,0 +1,21 @@
+import "next-auth";
+import "next-auth/jwt";
+
+declare module "next-auth" {
+  interface User {
+    id: string;
+  }
+  interface Session {
+    user: {
+      id: string;
+      name?: string | null;
+      email?: string | null;
+    };
+  }
+}
+
+declare module "next-auth/jwt" {
+  interface JWT {
+    id: string;
+  }
+}