feat: 添加日历批量操作与客户端时区感知功能，优化前端 UI 交互体验

apps/lib/core/api/api_exception.dart

@@ -22,7 +22,7 @@ abstract class ApiException implements Exception {
             (data['detail'] ?? data['message'] ?? data['error'])?.toString() ??
             '请求失败';
       } else {
-        detail = '请求失败';
+        detail = _networkErrorMessage(error);
       }
 
       final localized = _localizeError(detail, statusCode);
@@ -57,6 +57,21 @@ abstract class ApiException implements Exception {
     }
     return detail;
   }
+
+  static String _networkErrorMessage(DioException error) {
+    if (error.type == DioExceptionType.connectionTimeout ||
+        error.type == DioExceptionType.sendTimeout ||
+        error.type == DioExceptionType.receiveTimeout) {
+      return '网络超时，请确认手机与服务端在同一网络后重试';
+    }
+
+    if (error.type == DioExceptionType.connectionError ||
+        error.type == DioExceptionType.unknown) {
+      return '无法连接服务器。请在 iPhone 设置中为本应用开启“无线数据（WLAN与蜂窝网络）”，并确认本地网络权限已开启。';
+    }
+
+    return '请求失败';
+  }
 }
 
 class ServerException extends ApiException {