feat(shell): 桌面侧栏加 Account 一级项 + 顶栏通知铃铛 + invite/notifications 视图接线

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

client/lib/widgets/content_top_bar.dart

@@ -9,15 +9,24 @@ import '../pangolin_theme.dart';
 import '../state/app_providers.dart';
 import '../state/connection_provider.dart';
 import '../state/nodes_provider.dart';
+import 'notification_bell.dart';
 import 'pangolin_icons.dart';
 
 class ContentTopBar extends ConsumerWidget {
-  const ContentTopBar({super.key, required this.title, this.onBack, this.showThemeToggle = true, this.titleSize = 17});
+  const ContentTopBar({
+    super.key,
+    required this.title,
+    this.onBack,
+    this.showThemeToggle = true,
+    this.titleSize = 17,
+    this.onBell,
+  });
 
   final String title;
   final VoidCallback? onBack;
   final bool showThemeToggle;
   final double titleSize;
+  final VoidCallback? onBell;
 
   @override
   Widget build(BuildContext context, WidgetRef ref) {
@@ -52,6 +61,10 @@ class ContentTopBar extends ConsumerWidget {
             color: conn.phase == VpnPhase.on ? c.success : c.fg3,
           ),
         ),
+        if (onBell != null) ...[
+          const SizedBox(width: 12),
+          NotificationBell(onTap: onBell, hasUnread: true),
+        ],
         if (showThemeToggle) ...[
           const SizedBox(width: 12),
           InkWell(