fix(client): iOS 顶栏避开状态栏，修复菜单按钮被遮挡退不出登录

顶栏 Container 原从 y=0 起绘，iOS 状态栏盖住左上角菜单按钮，窄屏无法
打开抽屉菜单/退出登录。顶栏高度加上 MediaQuery.padding.top，内容下移
一个状态栏高度，蓝色仍铺满到屏幕顶。桌面/Web 状态栏高度为 0 不受影响。

todo #53。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/lib/screens/shell/app_shell.dart

@@ -155,6 +155,8 @@ class _AppShellState extends ConsumerState<AppShell> {
     final isOnline = ref.watch(connectivityProvider);
     final location = GoRouterState.of(context).matchedLocation;
     final isMobile = context.isMobile;
+    // iOS/刘海屏状态栏高度：顶栏需下移此距离，避免菜单按钮被状态栏遮挡
+    final topInset = MediaQuery.of(context).padding.top;
     final sidebarWidth = _sidebarExpanded ? 200.0 : 56.0;
     final updateNotifier = ref.watch(updateProvider.notifier);
     final updateInfo = ref.watch(updateProvider).valueOrNull;
@@ -169,11 +171,11 @@ class _AppShellState extends ConsumerState<AppShell> {
       drawerEnableOpenDragGesture: !kIsWeb && isMobile,
       body: Column(
         children: [
-          // Top Bar
+          // Top Bar（高度含状态栏内边距，蓝色铺满到屏幕顶，内容下移避开状态栏）
           Container(
-            height: 56,
+            height: 56 + topInset,
             color: AppTheme.primary,
-            padding: const EdgeInsets.symmetric(horizontal: 8),
+            padding: EdgeInsets.only(top: topInset, left: 8, right: 8),
             child: Row(
               children: [
                 IconButton(