feat(ui): add Restart worker menu entry under Help

Stops and starts the ClaudeDoWorker Windows service via
ServiceController. SignalR auto-reconnect plus the existing
ConnectionRestoredEvent handle the refresh, so the UI repopulates
counters and the active list once the worker is back up.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Ui/Views/MainWindow.axaml

@@ -67,6 +67,8 @@
                       Foreground="{DynamicResource TextDimBrush}">
               <MenuItem Header="Check for updates"
                         Command="{Binding CheckForUpdatesCommand}"/>
+              <MenuItem Header="Restart worker"
+                        Command="{Binding RestartWorkerCommand}"/>
               <MenuItem Header="About…" Command="{Binding OpenAboutCommand}"/>
             </MenuItem>
           </Menu>