Start adding Miniflux support plus other cleanup

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

Application/Options/BulkFeedWindow.xaml.cs

@@ -4,6 +4,7 @@ using System.Linq;
 using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Data;
+using FeedCenter.Feeds;
 
 namespace FeedCenter.Options;