feat(chat): 发收消息全量实现 (#25~#28)

- 移除 @riverpod/@freezed 注解依赖，全部改为手写 Provider（无需 build_runner）
  · LoginState 改为纯 Dart，LoginViewModel/ThemeViewModel/ChatViewModel 改为 Notifier
  · UserNotifier 改为 FamilyAsyncNotifier<User?,int>，mini_app_provider 改为手写 Provider
  · 15 个 StreamProvider/StreamProvider.family 从 @riverpod 迁移至手写

- 发送消息（#25）
  · SendMessageRequest/SendMessageResponse DTO
  · SendMessageUseCase：乐观写入 DB → HTTP POST → 更新 Chat 摘要

- 接收消息 WS（#26）
  · WsMessageService：监听 mode2 WS 帧 → HTTP 补拉 → DB 写入 → Chat 更新
  · FetchHistoryRequest/FetchHistoryResponse DTO（GET /app/api/chat/history）
  · FetchHistoryUseCase：拉取 → insertOrReplaceAll

- DI 装配（chat_service_providers.dart）
  · wsMessageServiceProvider、sendMessageUseCaseProvider、fetchHistoryUseCaseProvider

- 聊天列表页（#27）
  · ChatListViewModel（Notifier<void>）+ chat_page.dart 真实会话列表 UI
  · ListTile：头像首字母、最新消息摘要、未读角标、时间格式化

- 聊天详情页（#28）
  · ChatDetailViewModel（FamilyNotifier<ChatDetailState,int>）+ chat_detail_page.dart
  · 消息气泡（自己/他人分左右）、底部输入框、发送状态与错误提示

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/im_app/lib/features/mini_app/mini_app_provider.dart

@@ -1,25 +1,23 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:im_app/app/di/db_provider.dart';
 import 'package:im_app/data/repositories/discover_mini_app_repository_impl.dart';
 import 'package:im_app/data/repositories/explore_mini_app_repository_impl.dart';
 import 'package:im_app/data/repositories/favorite_mini_app_repository_impl.dart';
 import 'package:im_app/data/repositories/recent_mini_app_repository_impl.dart';
 import 'package:im_app/domain/repositories/mini_app_repository.dart';
-import 'package:riverpod_annotation/riverpod_annotation.dart';
 
-part 'mini_app_provider.g.dart';
+final discoverMiniAppRepositoryProvider = Provider<MiniAppRepository>(
+  (ref) => DiscoverMiniAppRepositoryImpl(ref.watch(storageSdkProvider)),
+);
 
-@riverpod
-MiniAppRepository discoverMiniAppRepository(Ref ref) =>
-    DiscoverMiniAppRepositoryImpl(ref.watch(storageSdkProvider));
+final exploreMiniAppRepositoryProvider = Provider<MiniAppRepository>(
+  (ref) => ExploreMiniAppRepositoryImpl(ref.watch(storageSdkProvider)),
+);
 
-@riverpod
-MiniAppRepository exploreMiniAppRepository(Ref ref) =>
-    ExploreMiniAppRepositoryImpl(ref.watch(storageSdkProvider));
+final favoriteMiniAppRepositoryProvider = Provider<MiniAppRepository>(
+  (ref) => FavoriteMiniAppRepositoryImpl(ref.watch(storageSdkProvider)),
+);
 
-@riverpod
-MiniAppRepository favoriteMiniAppRepository(Ref ref) =>
-    FavoriteMiniAppRepositoryImpl(ref.watch(storageSdkProvider));
-
-@riverpod
-MiniAppRepository recentMiniAppRepository(Ref ref) =>
-    RecentMiniAppRepositoryImpl(ref.watch(storageSdkProvider));
+final recentMiniAppRepositoryProvider = Provider<MiniAppRepository>(
+  (ref) => RecentMiniAppRepositoryImpl(ref.watch(storageSdkProvider)),
+);