feat: 设置区加开机自启动 CheckBox(默认勾选)

StartupManager 早就实现了,但之前:
1. 没 UI 入口 —— 用户得去注册表手动改
2. App.OnStartup 里只 EnableCurrentUserStartup,不 Disable —— 用户禁用了下次启动会被强制写回,改不掉

现在:

MainWindow.xaml 设置区(URL/Token 下方)加 CheckBox,跨两列:
- 标签:"开机自动启动(写入 HKCU\Software\Microsoft\Windows\CurrentVersion\Run,只对当前用户生效)"
- Tooltip 说明
- 初始状态从 config.Startup.Enabled 读

MainWindow.xaml.cs StartupCheckBox_Click:
- 勾选变化 → 改 _config.Startup.Enabled → 调 EnableCurrentUserStartup 或 DisableCurrentUserStartup → 异步 SaveAsync
- 状态条反馈 "已开启/关闭开机启动"
- 异常时状态条变 ErrorDot 红色

App.xaml.cs OnStartup 双向同步:
- config.Startup.Enabled=true → Enable
- config.Startup.Enabled=false → Disable
(之前是单向只 Enable,导致用户在 UI 禁用了重启又被写回)

config 是 source of truth,UI 改了立刻落盘 + 同步注册表,下次启动再 sync 一次保证一致。

MainWindow.xaml.cs

@@ -63,6 +63,7 @@ public partial class MainWindow : Window
 
         UrlTextBox.Text = config.Gotify.Url;
         TokenBox.Password = config.Gotify.ClientToken;
+        StartupCheckBox.IsChecked = config.Startup.Enabled;
         UpdateAppCount();
         SetStatus("等待连接", StatusKind.Pending);
         UpdateHistoryCount();
@@ -377,6 +378,35 @@ public partial class MainWindow : Window
         ThemeToggleButton.Content = ThemeService.Current == ThemeService.Dark ? "☾ 深色" : "☼ 浅色";
     }
 
+    private async void StartupCheckBox_Click(object sender, RoutedEventArgs e)
+    {
+        if (_config is null || _configService is null) return;
+
+        var enabled = StartupCheckBox.IsChecked == true;
+        _config.Startup.Enabled = enabled;
+
+        try
+        {
+            if (enabled)
+            {
+                Utils.StartupManager.EnableCurrentUserStartup(_logger!);
+                SetStatus("已开启开机启动", StatusKind.Connected);
+            }
+            else
+            {
+                Utils.StartupManager.DisableCurrentUserStartup(_logger!);
+                SetStatus("已关闭开机启动", StatusKind.Connected);
+            }
+            await _configService.SaveAsync(_config);
+            _logger?.Info($"Startup toggled. enabled={enabled}");
+        }
+        catch (Exception ex)
+        {
+            _logger?.Error("Toggle startup failed.", ex);
+            SetStatus($"切换开机启动失败:{ex.Message}", StatusKind.Error);
+        }
+    }
+
     private async void SaveButton_Click(object sender, RoutedEventArgs e)
     {
         if (_config is null || _configService is null) return;