新增：community feature 数据层——契约 v1.3.0 十九操作全覆盖 + ToggleSync 乐观更新状态机（T3-12）

- community_models：community/media 域 DTO 逐字段照冻结契约手写 JSON 映射
  （Post/FeedCard/PostComment/AuthorSummary 降级形态/媒体两步上传凭据等），
  未知枚举抛 FormatException 暴露契约漂移；CursorPage 上移 core 复用
- community_repository：13 路径 19 操作全覆盖；createPost/createComment
  必带 Idempotency-Key（每次逻辑提交换新键、刷新重放同键）；点赞/收藏/
  关注走 PUT/DELETE 语义幂等
- community_exceptions：v1.3.0 新增 9 码 + 40902 共码类型化异常映射
- toggle_sync：乐观翻转 + 快照回滚 + 单飞合并最终意图 + 代次守卫，
  点赞/收藏共用一套参数化状态机，权威终态对账收敛
- community_controller：Feed 多页缓存 + 首屏四态 + 尾部加载三态 +
  游标拼接 + 刷新代次丢弃旧尾页；详情副本与卡片互动状态同源；reset 清态
- app.dart 装配：community 服务分端口直连（:8084），共享 TokenRefresher，
  登出同步 reset
- 测试 286 → 347（模型映射 / 19 操作线路 / 错误映射 / 竞态序列全覆盖）

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/app/app.dart

@@ -12,6 +12,8 @@ import 'package:patbond_flutter/features/auth/auth_repository.dart';
 import 'package:patbond_flutter/features/auth/login_page.dart';
 import 'package:patbond_flutter/features/auth/session_manager.dart';
 import 'package:patbond_flutter/features/auth/splash_page.dart';
+import 'package:patbond_flutter/features/community/community_controller.dart';
+import 'package:patbond_flutter/features/community/community_repository.dart';
 import 'package:patbond_flutter/features/main/main_shell_page.dart';
 import 'package:patbond_flutter/features/pets/health_record_analytics.dart';
 import 'package:patbond_flutter/features/pets/pet_analytics.dart';
@@ -25,12 +27,14 @@ class App extends StatefulWidget {
     this.sessionManager,
     this.authRepository,
     this.petsRepository,
+    this.communityRepository,
   });
 
   /// 测试注入口；生产默认走安全存储 + 真实 API。
   final SessionManager? sessionManager;
   final AuthRepository? authRepository;
   final PetsRepository? petsRepository;
+  final CommunityRepository? communityRepository;
 
   @override
   State<App> createState() => _AppState();
@@ -41,6 +45,7 @@ class _AppState extends State<App> {
   late final SessionManager sessionManager;
   late final AuthRepository authRepository;
   late final PetsController petsController;
+  late final CommunityController communityController;
   late final PetAnalytics petAnalytics;
   late final HealthRecordAnalytics healthRecordAnalytics;
   late final SessionTracker _sessionTracker;
@@ -88,6 +93,10 @@ class _AppState extends State<App> {
     petsController = PetsController(
       repository: widget.petsRepository ?? _buildPetsRepository(),
     );
+    // T3-12 只装配数据层；Feed segment 的 UI 接线在 T3-14 挂入主壳。
+    communityController = CommunityController(
+      repository: widget.communityRepository ?? _buildCommunityRepository(),
+    );
     petAnalytics = PetAnalytics(_analytics.trackEvent);
     healthRecordAnalytics = HealthRecordAnalytics(_analytics.trackEvent);
 
@@ -143,6 +152,20 @@ class _AppState extends State<App> {
     return ApiPetsRepository(api: api);
   }
 
+  /// community 服务分端口直连（:8084），token 刷新单飞经共享 [TokenRefresher]。
+  CommunityRepository _buildCommunityRepository() {
+    final dio = buildPatbondDio(
+      session: sessionManager,
+      baseUrl: patbondCommunityApiBaseUrl,
+    );
+    final api = ApiClient(
+      dio: dio,
+      session: sessionManager,
+      refresher: _ensureRefresher(),
+    );
+    return ApiCommunityRepository(api: api);
+  }
+
   AnalyticsPageName? _resolveRootPage() {
     // 回栈到无名根路由时解析当前认证状态页/主壳 Tab
     return switch (sessionManager.status) {
@@ -153,9 +176,10 @@ class _AppState extends State<App> {
   }
 
   void _reportAuthStateChange() {
-    // 登出即清宠物档案内存副本（跨账号不泄漏；重登后列表页重新拉取）。
+    // 登出即清宠物档案与社区 Feed 内存副本（跨账号不泄漏；重登后重新拉取）。
     if (sessionManager.status == AuthStatus.unauthenticated) {
       petsController.reset();
+      communityController.reset();
     }
     // 认证状态机切页补点（03 §3.2 非路由曝光 1/2）
     final page = switch (sessionManager.status) {
@@ -173,6 +197,7 @@ class _AppState extends State<App> {
     WidgetsBinding.instance.removeObserver(_sessionTracker);
     appState.dispose();
     petsController.dispose();
+    communityController.dispose();
     if (widget.sessionManager == null) sessionManager.dispose();
     super.dispose();
   }