Restrcutured the database, and updated pipeline to include cover art.

MangaReader.Core/Data/SourceCover.cs

@@ -0,0 +1,14 @@
+namespace MangaReader.Core.Data;
+
+public class SourceCover
+{
+    public int SourceCoverId { get; set; }
+
+    public int MangaSourceId { get; set; }
+    public required MangaSource MangaSource { get; set; }
+
+    public required string Url { get; set; }
+
+    public int? MangaCoverId { get; set; }
+    public MangaCover? MangaCover { get; set; }
+}