Use UTC for AddedWhen timestamps in layout repository

Changed AddedWhen to use DateTime.UtcNow instead of DateTime.Now to ensure timestamps are stored in UTC, avoiding issues with local time zones.

DbFirst.Infrastructure/Repositories/LayoutRepository.cs

@@ -34,7 +34,7 @@ public class LayoutRepository : ILayoutRepository
                 UserName = userName,
                 LayoutData = layoutData,
                 AddedWho = userName,
-                AddedWhen = DateTime.Now
+                AddedWhen = DateTime.UtcNow
             };
             _db.SmfLayouts.Add(entity);
         }