Started the Split

Split Json data models coming from REST Api, from the Database models
storing them in a SQLite database.
Work to re-engineer endpoints to use Database objects, and copy/update
data from the json objects.
More work is needed.

FreeTubeSync/Model/Subscription.cs

@@ -1,19 +0,0 @@
-using System.ComponentModel.DataAnnotations;
-using System.Diagnostics.CodeAnalysis;
-
-namespace FreeTubeSync.Model;
-
-[SuppressMessage("ReSharper", "InconsistentNaming")]
-public class Subscription
-{
-    [Key]
-    public required string id { get; set; }
-    public required string name { get; set; }
-    public string? thumbnail { get; set; }
-
-    public void Update(Subscription other)
-    {
-        name = other.name;
-        thumbnail = other.thumbnail;
-    }
-}