Start adding Miniflux support plus other cleanup

- Modernize old async code
- Update to .NET 10
- Adjust namespace
- Bypass update check when debugging

Application/Options/FeedWindow.xaml.cs

@@ -14,7 +14,7 @@ public partial class FeedWindow
         InitializeComponent();
     }
 
-    public bool? Display(Feed feed, Window owner)
+    public bool? Display(Feeds.Feed feed, Window owner)
     {
         CategoryComboBox.ItemsSource = _entities.Categories;