Start adding Miniflux support plus other cleanup

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

Application/FeedParsers/FeedParserBase.cs

@@ -2,6 +2,7 @@
 using System;
 using System.Linq;
 using System.Xml;
+using FeedCenter.Feeds;
 
 namespace FeedCenter.FeedParsers;