Auto-set CreatedAt/UpdatedAt via EF interceptor; standardize timestamp names across entities

Application/Tracks/Responses/TrackApplicationResponse.cs

@@ -5,16 +5,16 @@ namespace Musify.Application.Tracks.Responses
     public record TrackApplicationResponse(
         Guid Id,
         string Title,
-        DateTime CreatedDate,
-        DateTime UpdatedDate)
+        DateTime CreatedAt,
+        DateTime UpdatedAt)
     {
         public static TrackApplicationResponse FromEntity(Track track)
         {
             return new TrackApplicationResponse(
                 track.Id,
                 track.Title,
-                track.CreatedDate,
-                track.UpdatedDate);
+                track.CreatedAt,
+                track.UpdatedAt);
         }
     }
 }