feat(locale): 实现 App 启动时语言和时区自动设置

- 新增系统语言/时区读取工具函数
- SessionStore 扩展支持时区存储
- 启动流程自动检测并保存系统语言/时区
- 注册时传递语言/时区到后端
- 登录后从服务器同步语言/时区

apps/lib/features/auth/presentation/bloc/auth_bloc.dart

@@ -50,8 +50,15 @@ class AuthBloc extends ChangeNotifier {
   Future<void> loginWithOtp({
     required String email,
     required String otp,
+    String? language,
+    String? timezone,
   }) async {
-    final user = await _repository.loginWithEmailOtp(email: email, otp: otp);
+    final user = await _repository.loginWithEmailOtp(
+      email: email,
+      otp: otp,
+      language: language,
+      timezone: timezone,
+    );
     _logger.info(message: 'User logged in', extra: {'user_id': user.id});
     _state = AuthState(status: AuthStatus.authenticated, user: user);
     notifyListeners();