feat: add database connections, initial migration and early CLI tooling

Entities/PlaylistUser.cs

@@ -0,0 +1,9 @@
+namespace Shadow.Entities;
+public class PlaylistUser
+{
+	required public int PlaylistId { get; set; }
+	required public int UserId { get; set; }
+
+	required public Playlist Playlist { get; set; }
+	required public User User { get; set; }
+}