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/Views/SettingsViewModel.cs

@@ -11,8 +11,9 @@ public partial class SettingsViewModel : ObservableObject
 {
     private readonly InstallContext _context;
     private readonly IReleaseClient _releases;
-    private readonly StopServiceStep _stopService;
-    private readonly StartServiceStep _startService;
+    private readonly StopWorkerStep _stopService;
+    private readonly StartWorkerStep _startService;
+    private readonly RegisterAutostartStep _registerAutostart;
     private readonly DownloadAndExtractStep _downloadStep;
     private readonly UninstallRunner _uninstallRunner;
 
@@ -37,8 +38,9 @@ public partial class SettingsViewModel : ObservableObject
         PageResolver resolver,
         InstallContext context,
         IReleaseClient releases,
-        StopServiceStep stopService,
-        StartServiceStep startService,
+        StopWorkerStep stopService,
+        StartWorkerStep startService,
+        RegisterAutostartStep registerAutostart,
         DownloadAndExtractStep downloadStep,
         UninstallRunner uninstallRunner)
     {
@@ -47,6 +49,7 @@ public partial class SettingsViewModel : ObservableObject
         _releases = releases;
         _stopService = stopService;
         _startService = startService;
+        _registerAutostart = registerAutostart;
         _downloadStep = downloadStep;
         _uninstallRunner = uninstallRunner;
         _selectedPage = Pages.FirstOrDefault();
@@ -154,7 +157,7 @@ public partial class SettingsViewModel : ObservableObject
         IsStatusError = false;
 
         var progress = new Progress<string>(msg => StatusMessage = msg);
-        var steps = new IInstallStep[] { _stopService, _downloadStep, _startService };
+        var steps = new IInstallStep[] { _stopService, _downloadStep, _registerAutostart, _startService };
 
         foreach (var step in steps)
         {