Feature: Add rich interactive Markdown renderer, wide adaptive memo panel, and custom language popover

src/app/register/page.tsx

@@ -1,10 +1,11 @@
-"use client";
+"use client";
 import { useState } from "react";
 import { signIn } from "next-auth/react";
 import { useRouter } from "next/navigation";
 import Link from "next/link";
-import { useI18n, Language } from "@/lib/i18n";
+import { useI18n } from "@/lib/i18n";
 import { useTheme } from "@/app/providers";
+import { LanguageSelector } from "@/components/ui/LanguageSelector";
 
 export default function RegisterPage() {
   const router = useRouter();
@@ -60,25 +61,7 @@ export default function RegisterPage() {
             <span className="auth-logo-name">{t("appName")}</span>
           </div>
           <div style={{ display: "flex", alignItems: "center", gap: 6 }}>
-            <select
-              aria-label={t("language")}
-              value={lang}
-              onChange={(e) => setLang(e.target.value as Language)}
-              style={{
-                background: "var(--bg-secondary)",
-                color: "var(--text-secondary)",
-                border: "1px solid var(--border)",
-                borderRadius: "var(--radius-xs)",
-                fontSize: 11,
-                padding: "3px 6px",
-                cursor: "pointer",
-                fontWeight: 600,
-              }}
-            >
-              <option value="en">EN</option>
-              <option value="ko">한국어</option>
-              <option value="ja">日本語</option>
-            </select>
+            <LanguageSelector />
 
             <button
               className="icon-btn"