feat(notification): 通知标题和正文支持多语言

- 通知静态配置支持 title/body i18n
- 前端通知列表和详情页展示本地化内容
- 新增数据库迁移脚本
- 更新通知协议文档

apps/lib/features/notifications/data/repositories/notification_repository.dart

@@ -6,11 +6,15 @@ abstract class NotificationRepository {
   Future<NotificationListResult> listNotifications({
     int limit = 20,
     String? cursor,
+    String locale = 'zh',
   });
 
   Future<int> getUnreadCount();
 
-  Future<NotificationItem> markRead({required String notificationId});
+  Future<NotificationItem> markRead({
+    required String notificationId,
+    String locale = 'zh',
+  });
 
   Future<int> markAllRead();
 }
@@ -25,8 +29,13 @@ class NotificationRepositoryImpl implements NotificationRepository {
   Future<NotificationListResult> listNotifications({
     int limit = 20,
     String? cursor,
+    String locale = 'zh',
   }) async {
-    return _notificationApi.listNotifications(limit: limit, cursor: cursor);
+    return _notificationApi.listNotifications(
+      limit: limit,
+      cursor: cursor,
+      locale: locale,
+    );
   }
 
   @override
@@ -35,8 +44,14 @@ class NotificationRepositoryImpl implements NotificationRepository {
   }
 
   @override
-  Future<NotificationItem> markRead({required String notificationId}) async {
-    return _notificationApi.markRead(notificationId: notificationId);
+  Future<NotificationItem> markRead({
+    required String notificationId,
+    String locale = 'zh',
+  }) async {
+    return _notificationApi.markRead(
+      notificationId: notificationId,
+      locale: locale,
+    );
   }
 
   @override