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>

tests/ClaudeDo.Installer.Tests/ScheduledTaskXmlTests.cs

@@ -0,0 +1,30 @@
+using ClaudeDo.Installer.Core;
+
+namespace ClaudeDo.Installer.Tests;
+
+public class ScheduledTaskXmlTests
+{
+    [Fact]
+    public void Build_EmbedsUserExeAndLogonTrigger()
+    {
+        var xml = ScheduledTaskXml.Build(
+            userId: "MACHINE\\mika",
+            workerExePath: @"C:\Program Files\ClaudeDo\worker\ClaudeDo.Worker.exe",
+            restartIntervalMinutes: 1);
+
+        Assert.Contains("<LogonTrigger>", xml);
+        Assert.Contains("<UserId>MACHINE\\mika</UserId>", xml);
+        Assert.Contains("<LogonType>InteractiveToken</LogonType>", xml);
+        Assert.Contains("<Hidden>true</Hidden>", xml);
+        Assert.Contains("<RunLevel>LeastPrivilege</RunLevel>", xml);
+        Assert.Contains(@"C:\Program Files\ClaudeDo\worker\ClaudeDo.Worker.exe", xml);
+        Assert.Contains("<Interval>PT1M</Interval>", xml);
+    }
+
+    [Fact]
+    public void Build_ClampsRestartIntervalToOneMinuteMinimum()
+    {
+        var xml = ScheduledTaskXml.Build("M\\u", @"C:\w.exe", restartIntervalMinutes: 0);
+        Assert.Contains("<Interval>PT1M</Interval>", xml);
+    }
+}