refactor(sidebar): 用户区域集成弹出菜单

- 移除原有的用户信息链接样式
- 集成 UserMenu 组件替代原有设计
- 支持主题切换、设置导航、登出等功能

src/components/layout/Sidebar.tsx

@@ -2,8 +2,8 @@
 
 import Link from 'next/link';
 import { usePathname, useRouter } from 'next/navigation';
-import { Plus, ChevronDown, PanelLeft, Trash2, MoreHorizontal, Loader2 } from 'lucide-react';
-import { Avatar } from '@/components/ui/Avatar';
+import { Plus, PanelLeft, Trash2, MoreHorizontal, Loader2 } from 'lucide-react';
+import { UserMenu } from '@/components/ui/UserMenu';
 import { cn } from '@/lib/utils';
 import { useConversations } from '@/hooks/useConversations';
 import { useSettings } from '@/hooks/useSettings';
@@ -164,19 +164,9 @@ export function Sidebar({ user, isOpen = true }: SidebarProps) {
           )}
         </nav>
 
-        {/* 用户信息 Footer */}
+        {/* 用户信息 Footer - 使用 UserMenu 弹出菜单 */}
         <footer className="p-4 border-t border-[var(--color-border-light)] mt-auto">
-          <Link
-            href="/settings"
-            className="flex items-center gap-3 p-2 rounded-lg cursor-pointer hover:bg-[var(--color-bg-hover)] transition-colors"
-          >
-            <Avatar name={user.name} size="md" />
-            <div className="flex-1 min-w-0">
-              <div className="text-sm text-[var(--color-text-primary)] truncate">{user.email}</div>
-              <div className="text-xs text-[var(--color-text-tertiary)] capitalize">{user.plan} plan</div>
-            </div>
-            <ChevronDown size={16} className="text-[var(--color-text-tertiary)]" />
-          </Link>
+          <UserMenu user={user} />
         </footer>
       </aside>