Remove Upsert functionality from Catalog API

Removed Upsert endpoint and related service/repository methods. Deleted ExecuteUpsertAsync helper. Insert now throws NotImplementedException as a placeholder. Refactored Delete method in repository; logic unchanged.

DbFirst.Domain/Repositories/ICatalogRepository.cs

@@ -8,6 +8,5 @@ public interface ICatalogRepository
     Task<VwmyCatalog?> GetByIdAsync(int id, CancellationToken cancellationToken = default);
     Task<VwmyCatalog> InsertAsync(VwmyCatalog catalog, CancellationToken cancellationToken = default);
     Task<VwmyCatalog?> UpdateAsync(int id, VwmyCatalog catalog, CancellationToken cancellationToken = default);
-    Task<VwmyCatalog?> UpsertAsync(VwmyCatalog catalog, CancellationToken cancellationToken = default);
     Task<bool> DeleteAsync(int id, CancellationToken cancellationToken = default);
 }