feat: Enable configurable proxy connection retry count

- Add Retry Count setting to SettingDialog
- Pass configured retry count to ProxyCheckerService
- Update default retry count to 5

Author: claude

Dialogs/Models/SettingModel.cs

@@ -19,6 +19,7 @@ public partial class SettingModel : ObservableObject, IDialogContext
     [ObservableProperty] private int _proxyType; // 0=HTTP, 1=SOCKS4, 2=SOCKS5
     [ObservableProperty] private int _timeout = 10; // 默认10秒
     [ObservableProperty] private int _concurrency = 50; // 默认50线程
+    [ObservableProperty] private int _retryCount = 5; // 默认重试1次
     [ObservableProperty] private bool _autoSave = true; // 默认自动保存
 
     public void Close()

Dialogs/Views/SettingDialog.axaml

@@ -46,6 +46,15 @@
                                     u:FormItem.Label="连接超时(秒)"
                                     ToolTip.Tip="代理连接超时时间" />
 
+                <u:NumericIntUpDown Width="100"
+                                    Minimum="0"
+                                    Maximum="10"
+                                    HorizontalAlignment="Left"
+                                    HorizontalContentAlignment="Center"
+                                    Value="{Binding RetryCount}"
+                                    u:FormItem.Label="重试次数"
+                                    ToolTip.Tip="连接失败后的重试次数" />
+
                 <CheckBox IsChecked="{Binding AutoSave}"
                           u:FormItem.Label="自动保存"
                           ToolTip.Tip="检测完成后自动保存结果到文件" />

ViewModels/MainViewModel.cs

@@ -371,7 +371,7 @@ private async Task StartAsync()
 
         ResetRunState();
         var ct = StartRun();
-        var service = new ProxyCheckerService(GlobalSetting.Instance.Setting.Timeout);
+        var service = new ProxyCheckerService(GlobalSetting.Instance.Setting.Timeout, GlobalSetting.Instance.Setting.RetryCount);
 
         try
         {