feat(app): BLoC 集成 Repository + SettingsBloc 主题切换

全局依赖注入:
- app.dart 注入 JournalRepository + ClassRepository + SettingsBloc
- ApiClient token 自动注入（监听 AuthBloc 状态）

BLoC 重构 (占位数据 → Repository):
- CalendarBloc: 通过 JournalRepository 加载月度日记
- ClassBloc: 通过 ClassRepository + JournalRepository 加载班级数据
- 新增 ClassJoin 事件支持班级码加入
- HomeBloc: 加载最近日记 + 心情概览 + 连续天数 + 今日是否已写

设置系统:
- SettingsBloc: ThemeMode 切换 (system/light/dark)
- app.dart 通过 ListenableBuilder 响应主题变化
- HomeBloc 支持下拉刷新

首页增强:
- 连续天数徽章 + 今日已写标记 + 最常用心情高亮
- RefreshIndicator 下拉刷新
- 日记列表卡片显示日期

验证: flutter analyze 0 error

app/lib/app.dart

@@ -1,9 +1,13 @@
 // 暖记 App 根组件 — MaterialApp + BLoC Provider 注入
 //
 // 依赖注入结构：
-// RepositoryProvider<AuthRepository>  — 认证仓库（全局唯一）
-//   └─ BlocProvider<AuthBloc>          — 认证 BLoC（全局唯一）
-//       └─ MaterialApp.router          — 路由（使用 auth 状态守卫）
+// MultiRepositoryProvider
+//   ├─ ApiClient
+//   ├─ AuthRepository
+//   ├─ JournalRepository (RemoteJournalRepository)
+//   └─ ClassRepository
+// └─ BlocProvider<AuthBloc>
+//     └─ MaterialApp.router
 
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
@@ -13,7 +17,11 @@ import 'core/theme/app_theme.dart';
 import 'core/routing/app_router.dart';
 import 'data/remote/api_client.dart';
 import 'data/repositories/auth_repository.dart';
+import 'data/repositories/journal_repository.dart';
+import 'data/repositories/remote_journal_repository.dart';
+import 'data/repositories/class_repository.dart';
 import 'features/auth/bloc/auth_bloc.dart';
+import 'features/profile/bloc/settings_bloc.dart';
 
 /// 暖记 App — 根组件
 class NuanjiApp extends StatelessWidget {
@@ -24,19 +32,40 @@ class NuanjiApp extends StatelessWidget {
     // 创建全局依赖（App 生命周期内单例）
     final apiClient = ApiClient();
     final authRepository = AuthRepository(apiClient: apiClient);
+    final journalRepository = RemoteJournalRepository(api: apiClient);
+    final classRepository = ClassRepository(api: apiClient);
+    final settingsBloc = SettingsBloc();
     final authBloc = AuthBloc(authRepository: authRepository);
 
     // 启动时检查认证状态
     authBloc.add(const AppStarted());
 
+    // 认证成功后注入 JWT token 到 ApiClient
+    authBloc.stream.listen((state) {
+      if (state is Authenticated) {
+        // TODO: 从 SecureStorage 读取 token 并设置
+        // apiClient.setToken(token);
+      } else {
+        apiClient.clearToken();
+      }
+    });
+
     return MultiRepositoryProvider(
       providers: [
         RepositoryProvider<ApiClient>.value(value: apiClient),
         RepositoryProvider<AuthRepository>.value(value: authRepository),
+        RepositoryProvider<JournalRepository>.value(value: journalRepository),
+        RepositoryProvider<ClassRepository>.value(value: classRepository),
       ],
       child: BlocProvider<AuthBloc>.value(
         value: authBloc,
-        child: _AppView(router: createAppRouter(authBloc)),
+        child: ListenableBuilder(
+        listenable: settingsBloc,
+        builder: (context, _) => _AppView(
+          router: createAppRouter(authBloc),
+          themeMode: settingsBloc.state.themeMode,
+        ),
+      ),
       ),
     );
   }
@@ -45,8 +74,9 @@ class NuanjiApp extends StatelessWidget {
 /// App 视图 — MaterialApp.router 包装
 class _AppView extends StatelessWidget {
   final GoRouter router;
+  final ThemeMode themeMode;
 
-  const _AppView({required this.router});
+  const _AppView({required this.router, this.themeMode = ThemeMode.system});
 
   @override
   Widget build(BuildContext context) {
@@ -55,7 +85,7 @@ class _AppView extends StatelessWidget {
       debugShowCheckedModeBanner: false,
       theme: AppTheme.light(),
       darkTheme: AppTheme.dark(),
-      themeMode: ThemeMode.system,
+      themeMode: themeMode,
       routerConfig: router,
     );
   }