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/apis/notification_api.dart

@@ -15,15 +15,19 @@ class NotificationApi {
   Future<NotificationListResult> listNotifications({
     int limit = 20,
     String? cursor,
+    String locale = 'zh',
   }) async {
-    final queryParts = <String>['limit=$limit'];
+    final queryParameters = <String, Object>{'limit': limit, 'locale': locale};
     if (cursor != null) {
-      queryParts.add('cursor=$cursor');
+      queryParameters['cursor'] = cursor;
     }
-    final path = '/api/v1/notifications?${queryParts.join("&")}';
 
     try {
-      final json = await _apiClient.getJson(path);
+      final response = await _apiClient.rawDio.get<Map<String, dynamic>>(
+        '/api/v1/notifications',
+        queryParameters: queryParameters,
+      );
+      final json = response.data ?? <String, dynamic>{};
       final itemsJson = json['items'] as List<dynamic>? ?? [];
       final items = itemsJson
           .map((e) => parseNotificationItem(e as Map<String, dynamic>))
@@ -59,21 +63,16 @@ class NotificationApi {
     }
   }
 
-  Future<NotificationItem> markRead({required String notificationId}) async {
-    _logger.info(
-      message: 'Mark read request started',
-      extra: {'notification_id': notificationId},
-    );
+  Future<NotificationItem> markRead({
+    required String notificationId,
+    String locale = 'zh',
+  }) async {
     try {
       final response = await _apiClient.rawDio.patch<Map<String, dynamic>>(
         '/api/v1/notifications/$notificationId/read',
+        queryParameters: {'locale': locale},
       );
-      final item = parseNotificationItem(response.data!);
-      _logger.info(
-        message: 'Mark read request succeeded',
-        extra: {'notification_id': notificationId, 'is_read': item.isRead},
-      );
-      return item;
+      return parseNotificationItem(response.data!);
     } on DioException catch (error, stackTrace) {
       _logger.error(
         message: 'Mark read failed',
@@ -85,17 +84,11 @@ class NotificationApi {
   }
 
   Future<int> markAllRead() async {
-    _logger.info(message: 'Mark all read request started');
     try {
       final response = await _apiClient.rawDio.patch<Map<String, dynamic>>(
         '/api/v1/notifications/mark-all-read',
       );
-      final updatedCount = response.data?['updatedCount'] as int? ?? 0;
-      _logger.info(
-        message: 'Mark all read request succeeded',
-        extra: {'updated_count': updatedCount},
-      );
-      return updatedCount;
+      return response.data?['updatedCount'] as int? ?? 0;
     } on DioException catch (error, stackTrace) {
       _logger.error(
         message: 'Mark all read failed',