feat: 更新導航欄指向新的複習頁面結構

- Navigation.tsx: 將複習連結從 /review-simple 更新為 /review
- Dashboard.tsx: 更新「開始今日複習」按鈕指向新的 /review 頁面
- 確保用戶界面統一指向正式複習頁面

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/app/dashboard/page.tsx

@@ -46,7 +46,7 @@ function DashboardContent() {
           <p className="text-gray-600">今天有 {stats.todayReview} 個單字等待複習，繼續加油！</p>
           <div className="mt-4 flex gap-3">
             <Link
-              href="/review-simple"
+              href="/review"
               className="bg-primary text-white px-6 py-2 rounded-lg font-medium hover:bg-primary-hover transition-colors"
             >
               開始今日複習

frontend/components/shared/Navigation.tsx

@@ -18,7 +18,7 @@ export function Navigation({ showExitLearning = false, onExitLearning }: Navigat
   const navItems = [
     { href: '/dashboard', label: '儀表板' },
     { href: '/flashcards', label: '詞卡' },
-    { href: '/review-simple', label: '複習' },
+    { href: '/review', label: '複習' },
     { href: '/generate', label: 'AI 生成' },
     { href: '/settings', label: '⚙️ 設定' }
   ]