Start adding Miniflux support plus other cleanup

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

Application/Options/FeedsOptionsPanel.xaml.cs

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