feat(worker): run worker as per-user logon task instead of Windows service

A LocalSystem Windows service can't see the logged-in user's Claude CLI
authentication, so the worker now runs as the current user via a hidden
per-user logon Scheduled Task with restart-on-failure.

- Worker is WinExe (no console window) with a Serilog rolling file sink and
  a single-instance mutex so the logon task, app ensure-running, and Restart
  button can't fight over the SignalR port.
- Installer replaces the service steps (register/start/stop) with autostart
  task steps, migrates the legacy ClaudeDoWorker service away on update, and
  removes the task on uninstall. ServicePage drops the service-account UI.
- UI gains a WorkerLocator; the app ensures the worker is running at startup
  and the Restart button kills+relaunches this install's worker process.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/ClaudeDo.Installer/Pages/ServicePage/ServicePageViewModel.cs

@@ -21,8 +21,6 @@ public partial class ServicePageViewModel : ObservableObject, IInstallerPage
     [ObservableProperty] private int _signalRPort = 47_821;
     [ObservableProperty] private int _queueBackstopIntervalMs = 30_000;
     [ObservableProperty] private string _claudeBin = "claude";
-    [ObservableProperty] private bool _isLocalSystem = true;
-    [ObservableProperty] private bool _isCurrentUser;
     [ObservableProperty] private bool _autoStart = true;
     [ObservableProperty] private int _restartDelayMs = 5000;
     [ObservableProperty] private string? _validationError;
@@ -43,7 +41,6 @@ public partial class ServicePageViewModel : ObservableObject, IInstallerPage
         _context.SignalRPort = SignalRPort;
         _context.QueueBackstopIntervalMs = QueueBackstopIntervalMs;
         _context.ClaudeBin = ClaudeBin;
-        _context.ServiceAccount = IsCurrentUser ? "CurrentUser" : "LocalSystem";
         _context.AutoStart = AutoStart;
         _context.RestartDelayMs = RestartDelayMs;
         _context.SignalRUrl = $"http://127.0.0.1:{SignalRPort}/hub";