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.Ui/Services/WorkerLocator.cs

@@ -0,0 +1,43 @@
+namespace ClaudeDo.Ui.Services;
+
+public sealed class WorkerLocator
+{
+    private const string InstallJson = "install.json";
+    private const string WorkerExe = "ClaudeDo.Worker.exe";
+    private const string WorkerSubdir = "worker";
+
+    public string? Find()
+        => FindByWalkingUp(AppContext.BaseDirectory)
+           ?? (OperatingSystem.IsWindows() ? FindByRegistry() : null);
+
+    public string? FindByWalkingUp(string startDir)
+    {
+        var dir = new DirectoryInfo(startDir);
+        while (dir is not null)
+        {
+            if (File.Exists(Path.Combine(dir.FullName, InstallJson)))
+            {
+                var candidate = Path.Combine(dir.FullName, WorkerSubdir, WorkerExe);
+                return File.Exists(candidate) ? candidate : null;
+            }
+            dir = dir.Parent;
+        }
+        return null;
+    }
+
+    [System.Runtime.Versioning.SupportedOSPlatform("windows")]
+    public string? FindByRegistry()
+    {
+        if (!OperatingSystem.IsWindows()) return null;
+        try
+        {
+            using var key = Microsoft.Win32.Registry.LocalMachine
+                .OpenSubKey(@"Software\Microsoft\Windows\CurrentVersion\Uninstall\ClaudeDo");
+            var location = key?.GetValue("InstallLocation") as string;
+            if (string.IsNullOrEmpty(location)) return null;
+            var candidate = Path.Combine(location, WorkerSubdir, WorkerExe);
+            return File.Exists(candidate) ? candidate : null;
+        }
+        catch { return null; }
+    }
+}