Update Show method to marshal to UI thread

Ensure notifications are shown on the UI thread.
Any caller that does notificationService.Show( ) or notificationService.TryAsync( ) from a background thread directly hits WindowNotificationManager.Show which hits line 48 raw with no UI thread marshalling. Leading to unhandled exception in Avalonia and crashes.

This follows the same pattern used by ShowAsyncCore which wraps every toast call in Dispatcher.UIThread.Invoke( ).

Without it, NotificationService.Show(INotification notification) on L48 is called from thread-pool threads (Polly continuations, Task.Run blocks) after HTTP failures exhaust retries and surface a notification.

Author: NeuralFault

StabilityMatrix.Avalonia/Services/NotificationService.cs

@@ -45,10 +45,18 @@ public void Initialize(
         };
     }
 
-    public void Show(INotification notification)
+   public void Show(INotification notification)
+{
+    // Must marshal to UI thread - WindowNotificationManager requires it
+    if (Dispatcher.UIThread.CheckAccess())
     {
         notificationManager?.Show(notification);
     }
+    else
+    {
+        Dispatcher.UIThread.Post(() => notificationManager?.Show(notification));
+    }
+}
 
     /// <inheritdoc />
     public Task ShowPersistentAsync(NotificationKey key, DesktopNotifications.Notification notification)