feat: 实现站内通知系统

- 后端: 新增 notifications/user_notifications 表迁移及 ORM 模型
- 后端: 实现 schema/repository/service/router 全套通知 API
  - GET /api/v1/notifications (列表+游标分页)
  - GET /api/v1/notifications/unread-count
  - PATCH /api/v1/notifications/{id}/read (幂等)
  - PATCH /api/v1/notifications/mark-all-read (幂等)
- 后端: payload 使用 Pydantic discriminated union (none/open_route/open_url)
- 后端: 19 个单元测试全部通过
- Flutter: 通知 feature 完整实现 (models/apis/repositories/bloc/UI)
- Flutter: Home 页通知按钮接入真实页面，显示未读 badge
- Flutter: 14 个测试全部通过
- 协议文档: notification-inbox-protocol.md 及错误码注册

apps/lib/features/home/presentation/screens/home_screen.dart

@@ -8,6 +8,9 @@ import '../../../divination/presentation/screens/divination_result_screen.dart';
 import '../../../divination/data/apis/divination_api.dart';
 import '../../../divination/data/models/divination_params.dart';
 import '../../../divination/data/models/divination_result.dart';
+import '../../../notifications/data/repositories/notification_repository.dart';
+import '../../../notifications/presentation/bloc/notification_bloc.dart';
+import '../../../notifications/presentation/screens/notification_center_screen.dart';
 import '../../../settings/data/models/profile_settings.dart';
 import '../../../settings/presentation/screens/settings_screen.dart';
 import '../../../../l10n/app_localizations.dart';
@@ -15,8 +18,6 @@ import '../../../../shared/theme/app_color_palette.dart';
 import '../../../../shared/theme/design_tokens.dart';
 import '../../../../shared/widgets/bottom_nav_bar.dart';
 import '../../../../shared/widgets/divination/divination_summary_card.dart';
-import '../../../../shared/widgets/toast/toast.dart';
-import '../../../../shared/widgets/toast/toast_type.dart';
 
 class HomeScreen extends StatefulWidget {
   const HomeScreen({
@@ -28,6 +29,8 @@ class HomeScreen extends StatefulWidget {
     required this.historyRecords,
     required this.coinBalance,
     required this.divinationApi,
+    required this.notificationBloc,
+    required this.notificationRepository,
     required this.onLocaleChanged,
     required this.onProfileSettingsChanged,
     required this.onSaveProfile,
@@ -45,6 +48,8 @@ class HomeScreen extends StatefulWidget {
   final List<DivinationResultData> historyRecords;
   final int coinBalance;
   final DivinationApi divinationApi;
+  final NotificationBloc notificationBloc;
+  final NotificationRepository notificationRepository;
   final Future<void> Function(String languageTag) onLocaleChanged;
   final Future<void> Function(ProfileSettingsV1 settings)
   onProfileSettingsChanged;
@@ -108,6 +113,8 @@ class _HomeScreenState extends State<HomeScreen> {
             onDivinationCompleted: widget.onDivinationCompleted,
             onDeleteHistorySession: widget.onDeleteHistorySession,
             allowVibration: widget.profileSettings.notification.allowVibration,
+            notificationBloc: widget.notificationBloc,
+            notificationRepository: widget.notificationRepository,
           ),
           _ProfileTab(
             account: widget.account,
@@ -155,6 +162,8 @@ class _HomeTab extends StatelessWidget {
     required this.onDivinationCompleted,
     required this.onDeleteHistorySession,
     required this.allowVibration,
+    required this.notificationBloc,
+    required this.notificationRepository,
   });
 
   final List<DivinationResultData> historyItems;
@@ -165,6 +174,8 @@ class _HomeTab extends StatelessWidget {
   onDivinationCompleted;
   final Future<void> Function(String threadId) onDeleteHistorySession;
   final bool allowVibration;
+  final NotificationBloc notificationBloc;
+  final NotificationRepository notificationRepository;
 
   @override
   Widget build(BuildContext context) {
@@ -194,16 +205,34 @@ class _HomeTab extends StatelessWidget {
                   ),
                   IconButton(
                     onPressed: () {
-                      Toast.show(
-                        context,
-                        l10n.featurePending,
-                        type: ToastType.info,
+                      Navigator.of(context).push(
+                        MaterialPageRoute<void>(
+                          builder: (_) => NotificationCenterScreen(
+                            repository: notificationRepository,
+                          ),
+                        ),
                       );
                     },
-                    icon: Icon(
-                      Icons.notifications,
-                      color: colors.primary,
-                      size: 28,
+                    icon: ListenableBuilder(
+                      listenable: notificationBloc,
+                      builder: (context, _) {
+                        final count = notificationBloc.state.unreadCount;
+                        if (count > 0) {
+                          return Badge(
+                            label: Text(count > 99 ? '99+' : '$count'),
+                            child: Icon(
+                              Icons.notifications,
+                              color: colors.primary,
+                              size: 28,
+                            ),
+                          );
+                        }
+                        return Icon(
+                          Icons.notifications,
+                          color: colors.primary,
+                          size: 28,
+                        );
+                      },
                     ),
                     tooltip: l10n.notify,
                   ),