Phase 1: versioning, menu bar, About dialog, right-click context menu

- Directory.Build.props sets Version=0.1.0 (semver pre-1.0 = beta) plus
  Authors / Product / RepositoryUrl, picked up by all three projects.
- MainWindow gets a real menu bar (File / Server / Help) replacing the
  old toolbar. File: New endpoint / Import / Export / Backups (last
  three are stubs for the next phase) / Exit. Server: Settings /
  Restart service. Help: About.
- Drop the Refresh button - the 3 s polling loop covers it.
- DataGridRow gets a right-click context menu: Edit / Copy URL /
  toggle Enabled / Delete.
- New About dialog reads AssemblyInformationalVersion at runtime and
  links jpaul.me + the GitHub repo via clickable hyperlinks.
- Ctrl+N input binding for new-endpoint.

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

src/WebhookServer.Gui/ViewModels/MainViewModel.cs

@@ -175,6 +175,41 @@ public sealed partial class MainViewModel : ObservableObject
         }
     }
 
+    [RelayCommand]
+    private async Task RestartServiceAsync()
+    {
+        var ok = MessageBox.Show(
+            "Restart the WebhookServer service? In-flight requests will be aborted.",
+            "Restart service",
+            MessageBoxButton.OKCancel,
+            MessageBoxImage.Warning);
+        if (ok != MessageBoxResult.OK) return;
+
+        try
+        {
+            await _client.RestartListenerAsync().ConfigureAwait(false);
+            await Task.Delay(2000).ConfigureAwait(false);
+            await RefreshAsync().ConfigureAwait(false);
+        }
+        catch (Exception ex)
+        {
+            ShowError("Restart failed", ex);
+        }
+    }
+
+    [RelayCommand]
+    private void ShowAbout()
+    {
+        var dlg = new Views.AboutDialog { Owner = Application.Current.MainWindow };
+        dlg.ShowDialog();
+    }
+
+    [RelayCommand]
+    private void Exit()
+    {
+        Application.Current.Shutdown();
+    }
+
     [RelayCommand]
     private void CopyEndpointUrl()
     {