fix: 修复 Flutter Web 白屏问题

- main.dart: 添加全局错误处理和 FlutterError.onError
- index.html: 添加加载指示器，vconsole 仅在开发环境启用
- dio_client.dart: 添加详细错误日志，优化超时配置

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

flutter_monisuo/lib/core/network/dio_client.dart

@@ -1,4 +1,5 @@
 import 'package:dio/dio.dart';
+import 'package:flutter/foundation.dart';
 import '../constants/api_endpoints.dart';
 import '../storage/local_storage.dart';
 import 'api_exception.dart';
@@ -7,8 +8,9 @@ import 'api_response.dart';
 /// 网络配置常量
 class NetworkConfig {
   static const String baseUrl = ApiEndpoints.baseUrl;
-  static const Duration connectTimeout = Duration(seconds: 30);
-  static const Duration receiveTimeout = Duration(seconds: 30);
+  static const Duration connectTimeout = Duration(seconds: 15);
+  static const Duration receiveTimeout = Duration(seconds: 15);
+  static const Duration sendTimeout = Duration(seconds: 15);
 }
 
 /// Dio 网络客户端
@@ -18,6 +20,7 @@ class DioClient {
   DioClient() {
     _dio = _createDio();
     _setupInterceptors();
+    debugPrint('DioClient initialized with baseUrl: ${NetworkConfig.baseUrl}');
   }
 
   Dio _createDio() {
@@ -25,6 +28,7 @@ class DioClient {
       baseUrl: NetworkConfig.baseUrl,
       connectTimeout: NetworkConfig.connectTimeout,
       receiveTimeout: NetworkConfig.receiveTimeout,
+      sendTimeout: NetworkConfig.sendTimeout,
       headers: {'Content-Type': 'application/json'},
     ));
   }
@@ -32,11 +36,7 @@ class DioClient {
   void _setupInterceptors() {
     _dio.interceptors.addAll([
       _AuthInterceptor(),
-      LogInterceptor(
-        requestHeader: false,
-        responseHeader: false,
-        error: true,
-      ),
+      _LoggingInterceptor(),
     ]);
   }
 
@@ -80,6 +80,15 @@ class DioClient {
   }
 
   ApiResponse<T> _handleError<T>(DioException e) {
+    // 详细错误日志
+    debugPrint('=== Network Error ===');
+    debugPrint('Type: ${e.type}');
+    debugPrint('Message: ${e.message}');
+    debugPrint('URL: ${e.requestOptions.uri}');
+    debugPrint('StatusCode: ${e.response?.statusCode}');
+    debugPrint('ResponseData: ${e.response?.data}');
+    debugPrint('====================');
+
     if (_isUnauthorized(e)) {
       _clearUserData();
       return ApiResponse.unauthorized('登录已过期，请重新登录');
@@ -106,15 +115,55 @@ class DioClient {
       case DioExceptionType.receiveTimeout:
         return '响应超时，请重试';
       case DioExceptionType.connectionError:
-        return '网络连接失败';
+        return '网络连接失败，请检查网络设置';
       case DioExceptionType.badResponse:
-        return '服务器错误 (${e.response?.statusCode})';
+        final statusCode = e.response?.statusCode;
+        if (statusCode == 500) {
+          return '服务器内部错误';
+        } else if (statusCode == 502 || statusCode == 503) {
+          return '服务暂时不可用';
+        }
+        return '服务器错误 ($statusCode)';
       default:
         return e.message ?? '网络请求失败';
     }
   }
 }
 
+/// 日志拦截器
+class _LoggingInterceptor extends Interceptor {
+  @override
+  void onRequest(RequestOptions options, RequestInterceptorHandler handler) {
+    debugPrint('┌──────────────────────────────────────────────────────────');
+    debugPrint('│ REQUEST: ${options.method} ${options.uri}');
+    debugPrint('│ Headers: ${options.headers}');
+    if (options.data != null) {
+      debugPrint('│ Data: ${options.data}');
+    }
+    debugPrint('└──────────────────────────────────────────────────────────');
+    super.onRequest(options, handler);
+  }
+
+  @override
+  void onResponse(Response response, ResponseInterceptorHandler handler) {
+    debugPrint('┌──────────────────────────────────────────────────────────');
+    debugPrint('│ RESPONSE: ${response.statusCode} ${response.requestOptions.uri}');
+    debugPrint('│ Data: ${response.data}');
+    debugPrint('└──────────────────────────────────────────────────────────');
+    super.onResponse(response, handler);
+  }
+
+  @override
+  void onError(DioException err, ErrorInterceptorHandler handler) {
+    debugPrint('┌──────────────────────────────────────────────────────────');
+    debugPrint('│ ERROR: ${err.type} ${err.requestOptions.uri}');
+    debugPrint('│ Message: ${err.message}');
+    debugPrint('│ StatusCode: ${err.response?.statusCode}');
+    debugPrint('└──────────────────────────────────────────────────────────');
+    super.onError(err, handler);
+  }
+}
+
 /// 认证拦截器
 class _AuthInterceptor extends Interceptor {
   @override