feat(notif): 通知占位屏 + 移动顶栏铃铛(Spec ③接口占位)

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

client/lib/screens/account_page.dart

@@ -11,8 +11,10 @@ import '../state/auth_provider.dart';
 import '../state/navigation_provider.dart';
 import '../widgets/account_screens.dart';
 import '../widgets/app_top_bar.dart';
+import '../widgets/notification_bell.dart';
 import '../widgets/pangolin_icons.dart';
 import 'invite_page.dart';
+import 'notifications_page.dart';
 import 'orders_page.dart';
 import 'payment_page.dart';
 import 'purchase_page.dart';
@@ -129,7 +131,13 @@ class AccountPage extends ConsumerWidget {
 
     if (isWide) return body;
     return Column(crossAxisAlignment: CrossAxisAlignment.start, children: [
-      AppTopBar(brand: t.brand),
+      AppTopBar(
+        brand: t.brand,
+        trailing: NotificationBell(
+          hasUnread: true,
+          onTap: () => open(NavView.notifications, NotificationsScreen(t: t)),
+        ),
+      ),
       PageTitle(title: t.meTitle),
       Expanded(child: body),
     ]);