feat(client): main 接入可切换三主题（启动恢复持久化选择）

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/lib/main.dart

@@ -10,7 +10,8 @@ import 'core/config/app_info.dart';
 import 'core/errors/error_reporter.dart';
 import 'core/platform/single_instance.dart' as single_instance;
 import 'core/router/app_router.dart';
-import 'core/theme/app_theme.dart';
+import 'core/theme/theme_controller.dart';
+import 'core/theme/themes.dart';
 import 'providers/connectivity_provider.dart';
 
 void main() {
@@ -99,6 +100,7 @@ class _JiuAppState extends ConsumerState<JiuApp> {
     // 路由 redirect 在 initialized=false 时返回 null（不重定向），
     // 初始化完成后 authState 变化触发 router refresh，redirect 重新执行
     WidgetsBinding.instance.addPostFrameCallback((_) async {
+      await ref.read(themeControllerProvider.notifier).restore();
       await ref.read(authStateProvider.notifier).restore();
       await ref.read(connectivityProvider.notifier).forceCheck();
     });
@@ -107,9 +109,10 @@ class _JiuAppState extends ConsumerState<JiuApp> {
   @override
   Widget build(BuildContext context) {
     final router = ref.watch(appRouterProvider);
+    final themeKey = ref.watch(themeControllerProvider);
     return MaterialApp.router(
       title: kDebugMode ? '岩美 [DEBUG]' : '岩美',
-      theme: AppTheme.light(),
+      theme: buildTheme(themeKey),
       routerConfig: router,
       debugShowCheckedModeBanner: false,
       localizationsDelegates: const [