feat(app): D.3 中等优先级 UX 改进 — 保存指示器 + 触摸目标 + 主题持久化

D.3.2 三态保存指示器:
- 未保存 (灰色) → 保存中 (琥珀色脉冲点) → 已保存 (绿色点)
- _PulsingDot 动画组件，800ms 呼吸效果
- 点击'完成'时显示保存中状态

D.3.3 工具栏触摸目标:
- BoxConstraints 36x36 → 44x44，符合 WCAG 标准

D.3.4 主题偏好持久化:
- SettingsBloc 接受 SharedPreferences，保存/恢复 themeMode
- NuanjiApp 改为 StatefulWidget，异步初始化 SharedPreferences
- 启动时显示 loading，初始化完成后渲染 app

app/lib/app.dart

@@ -15,6 +15,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:go_router/go_router.dart';
 import 'package:provider/provider.dart' show ListenableProvider;
+import 'package:shared_preferences/shared_preferences.dart';
 
 import 'config/app_config.dart';
 import 'core/theme/app_theme.dart';
@@ -31,70 +32,99 @@ import 'features/auth/bloc/auth_bloc.dart';
 import 'features/profile/bloc/settings_bloc.dart';
 
 /// 暖记 App — 根组件
-class NuanjiApp extends StatelessWidget {
+class NuanjiApp extends StatefulWidget {
   const NuanjiApp({super.key});
 
   @override
-  Widget build(BuildContext context) {
+  State<NuanjiApp> createState() => _NuanjiAppState();
-    // 创建全局依赖（App 生命周期内单例）
+}
-    // 开发模式默认使用 localhost，可通过 --dart-define 覆盖
+
+class _NuanjiAppState extends State<NuanjiApp> {
+  late final ApiClient _apiClient;
+  late final AuthRepository _authRepository;
+  late final JournalRepository _journalRepository;
+  late final RemoteJournalRepository _remoteJournalRepository;
+  late final SyncEngine _syncEngine;
+  late final ClassRepository _classRepository;
+  late final SettingsBloc _settingsBloc;
+  late final AuthBloc _authBloc;
+
+  bool _initialized = false;
+
+  @override
+  void initState() {
+    super.initState();
+    _initApp();
+  }
+
+  Future<void> _initApp() async {
     final config = kDebugMode ? AppConfig.dev : AppConfig.fromEnvironment();
-    final apiClient = ApiClient(baseUrl: config.apiBaseUrl);
+    _apiClient = ApiClient(baseUrl: config.apiBaseUrl);
     final tokenStore = createSecureTokenStore();
-    final authRepository = AuthRepository(apiClient: apiClient, tokenStore: tokenStore);
+    _authRepository = AuthRepository(apiClient: _apiClient, tokenStore: tokenStore);
-    // 离线优先：Isar 为主要本地仓库，Remote 供 SyncEngine 推送
+    _journalRepository = kIsWeb
-    // Web 平台：Isar 3.x 不支持 Web，直接使用远程仓库
+        ? RemoteJournalRepository(api: _apiClient)
-    final journalRepository = kIsWeb
-        ? RemoteJournalRepository(api: apiClient)
         : IsarJournalRepository();
-    final remoteJournalRepository = RemoteJournalRepository(api: apiClient);
+    _remoteJournalRepository = RemoteJournalRepository(api: _apiClient);
-    final syncEngine = SyncEngine(apiClient: apiClient);
+    _syncEngine = SyncEngine(apiClient: _apiClient);
-    final classRepository = ClassRepository(api: apiClient);
+    _classRepository = ClassRepository(api: _apiClient);
-    final settingsBloc = SettingsBloc();
+    _settingsBloc = SettingsBloc(
-    final authBloc = AuthBloc(
+      prefs: await SharedPreferences.getInstance(),
-      authRepository: authRepository,
+    );
-      classRepository: classRepository,
+    _authBloc = AuthBloc(
+      authRepository: _authRepository,
+      classRepository: _classRepository,
     );
 
     // 启动时检查认证状态
-    authBloc.add(const AppStarted());
+    _authBloc.add(const AppStarted());
 
-    // 异步恢复 SyncEngine 持久化队列（fire-and-forget，不阻塞 UI）
+    // 异步恢复 SyncEngine 持久化队列
-    syncEngine.restorePendingQueue();
+    _syncEngine.restorePendingQueue();
-    // 启动网络监听 — 网络恢复时自动触发 trySync()
+    _syncEngine.startAutoSync();
-    syncEngine.startAutoSync();
 
     // 认证状态监听：登出时清除 token
-    // 注意：登录时 token 由 AuthRepository.login() 直接注入 ApiClient
+    _authBloc.stream.listen((state) {
-    authBloc.stream.listen((state) {
       if (state is! Authenticated) {
-        apiClient.clearToken();
+        _apiClient.clearToken();
       }
     });
 
-    // Token 刷新彻底失败时 → 派发 AuthExpired → 路由重定向到登录页
+    // Token 刷新彻底失败时 → 派发 AuthExpired
-    apiClient.onAuthFailed = () {
+    _apiClient.onAuthFailed = () {
-      authBloc.add(const AuthExpired());
+      _authBloc.add(const AuthExpired());
     };
 
+    setState(() => _initialized = true);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    if (!_initialized) {
+      return const MaterialApp(
+        debugShowCheckedModeBanner: false,
+        home: Scaffold(body: Center(child: CircularProgressIndicator())),
+      );
+    }
+
     return MultiRepositoryProvider(
       providers: [
-        RepositoryProvider<ApiClient>.value(value: apiClient),
+        RepositoryProvider<ApiClient>.value(value: _apiClient),
-        RepositoryProvider<AuthRepository>.value(value: authRepository),
+        RepositoryProvider<AuthRepository>.value(value: _authRepository),
-        RepositoryProvider<JournalRepository>.value(value: journalRepository),
+        RepositoryProvider<JournalRepository>.value(value: _journalRepository),
-        RepositoryProvider<RemoteJournalRepository>.value(value: remoteJournalRepository),
+        RepositoryProvider<RemoteJournalRepository>.value(value: _remoteJournalRepository),
-        RepositoryProvider<SyncEngine>.value(value: syncEngine),
+        RepositoryProvider<SyncEngine>.value(value: _syncEngine),
-        RepositoryProvider<ClassRepository>.value(value: classRepository),
+        RepositoryProvider<ClassRepository>.value(value: _classRepository),
       ],
       child: ListenableProvider<SettingsBloc>.value(
-        value: settingsBloc,
+        value: _settingsBloc,
         child: Builder(
           builder: (context) {
             final settings = context.watch<SettingsBloc>();
             return BlocProvider<AuthBloc>.value(
-              value: authBloc,
+              value: _authBloc,
               child: _AppView(
-                router: createAppRouter(authBloc),
+                router: createAppRouter(_authBloc),
                 themeMode: settings.state.themeMode,
               ),
             );

app/lib/features/editor/views/editor_page.dart

@@ -337,6 +337,9 @@ class _EditorViewState extends State<_EditorView> {
   /// 查看模式：打开已有日记时默认只读，点击"编辑"后进入编辑模式
   bool _isViewMode = false;
 
+  /// 保存中状态 — 用于显示"保存中..."指示器
+  bool _isSaving = false;
+
   @override
   void initState() {
     super.initState();
@@ -595,9 +598,16 @@ class _EditorViewState extends State<_EditorView> {
     );
   }
 
-  /// 保存处理
+  /// 保存处理 — 显示"保存中..."后触发保存
   void _handleSave(BuildContext context, EditorState state) {
-    widget.onSaveComplete();
+    setState(() => _isSaving = true);
+    // 短暂延迟让 UI 显示"保存中..."状态
+    Future.delayed(const Duration(milliseconds: 300), () {
+      if (mounted) {
+        setState(() => _isSaving = false);
+        widget.onSaveComplete();
+      }
+    });
   }
 
   /// 显示评论列表
@@ -624,7 +634,26 @@ class _EditorViewState extends State<_EditorView> {
   }
 
   /// 自动保存状态指示器
+  /// 保存指示器 — 三态: 未保存 / 保存中 / 已保存
   Widget _buildAutosaveIndicator(EditorState state) {
+    // 保存中 — 琥珀色脉冲点
+    if (_isSaving) {
+      return Padding(
+        padding: const EdgeInsets.symmetric(horizontal: 4),
+        child: Row(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            _PulsingDot(color: AppColors.tertiary),
+            const SizedBox(width: 4),
+            Text(
+              '保存中...',
+              style: TextStyle(fontSize: 11, color: Colors.amber[700]),
+            ),
+          ],
+        ),
+      );
+    }
+    // 未保存
     if (state.lastSavedAt == null) {
       return Padding(
         padding: const EdgeInsets.symmetric(horizontal: 4),
@@ -634,6 +663,7 @@ class _EditorViewState extends State<_EditorView> {
         ),
       );
     }
+    // 已保存 — 绿色点
     return Padding(
       padding: const EdgeInsets.symmetric(horizontal: 4),
       child: Row(
@@ -1211,3 +1241,53 @@ class _ImageSourceButton extends StatelessWidget {
     );
   }
 }
+
+/// 脉冲圆点动画 — 用于"保存中..."指示器
+class _PulsingDot extends StatefulWidget {
+  const _PulsingDot({required this.color});
+  final Color color;
+
+  @override
+  State<_PulsingDot> createState() => _PulsingDotState();
+}
+
+class _PulsingDotState extends State<_PulsingDot>
+    with SingleTickerProviderStateMixin {
+  late final AnimationController _controller;
+
+  @override
+  void initState() {
+    super.initState();
+    _controller = AnimationController(
+      vsync: this,
+      duration: const Duration(milliseconds: 800),
+    )..repeat(reverse: true);
+  }
+
+  @override
+  void dispose() {
+    _controller.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return AnimatedBuilder(
+      animation: _controller,
+      builder: (context, _) {
+        final scale = 0.6 + 0.4 * _controller.value;
+        return Transform.scale(
+          scale: scale,
+          child: Container(
+            width: 6,
+            height: 6,
+            decoration: BoxDecoration(
+              color: widget.color,
+              shape: BoxShape.circle,
+            ),
+          ),
+        );
+      },
+    );
+  }
+}

app/lib/features/editor/widgets/editor_toolbar.dart

@@ -71,7 +71,7 @@ class EditorToolbar extends StatelessWidget {
       onTap: () => onEvent(isActive ? ToolReactivated(tool) : ToolChanged(tool)),
       behavior: HitTestBehavior.opaque,
       child: Container(
-        constraints: const BoxConstraints(minWidth: 36, minHeight: 36),
+        constraints: const BoxConstraints(minWidth: 44, minHeight: 44),
         padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 4),
         child: Column(
           mainAxisSize: MainAxisSize.min,

app/lib/features/profile/bloc/settings_bloc.dart

@@ -1,9 +1,12 @@
 // 设置 BLoC — 主题切换 + 应用设置管理
 //
 // ChangeNotifier 模式（同 MoodBloc），通过 ListenableBuilder 消费。
-// Phase 1: 内存态 + TODO 持久化到 SharedPreferences。
+// 主题偏好持久化到 SharedPreferences。
 
 import 'package:flutter/material.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+const _kThemeMode = 'settings_theme_mode';
 
 // ===== State =====
 
@@ -28,14 +31,34 @@ class SettingsState {
 
 /// 设置管理器 — 全局单例，在 NuanjiApp 中创建
 class SettingsBloc extends ChangeNotifier {
+  SettingsBloc({SharedPreferences? prefs}) : _prefs = prefs {
+    _loadSavedTheme();
+  }
+
+  final SharedPreferences? _prefs;
   SettingsState _state = const SettingsState();
   SettingsState get state => _state;
 
+  /// 从 SharedPreferences 恢复保存的主题
+  void _loadSavedTheme() {
+    if (_prefs == null) return;
+    final saved = _prefs?.getString(_kThemeMode);
+    if (saved != null) {
+      final mode = switch (saved) {
+        'light' => ThemeMode.light,
+        'dark' => ThemeMode.dark,
+        _ => ThemeMode.system,
+      };
+      _state = _state.copyWith(themeMode: mode);
+      notifyListeners();
+    }
+  }
+
   /// 切换主题模式
   void changeTheme(ThemeMode mode) {
     _state = _state.copyWith(themeMode: mode);
     notifyListeners();
-    // TODO: 持久化到 SharedPreferences
+    _prefs?.setString(_kThemeMode, mode.name);
   }
 
   /// 循环切换: system → light → dark → system