refactor: replace internal UnitOfWork with NotificationUnitOfWork and NotificationBaseRepository

- Consolidate unit of work implementation with NotificationUnitOfWork.
- Refactor repositories to use NotificationBaseRepository for consistency.
- Simplify request handlers by removing IUnitOfWork dependency.
- Update related tests and service registration.

HrynCo.NotificationService.Services/EmailTemplates/Delete/DeleteEmailTemplateHandler.cs

@@ -13,9 +13,8 @@ internal sealed class DeleteEmailTemplateHandler
 
     public DeleteEmailTemplateHandler(
         IContextualSerilogLogger<DeleteEmailTemplateCommand> logger,
-        IUnitOfWork unitOfWork,
         IEmailTemplateRepository templates)
-        : base(logger, unitOfWork)
+        : base(logger)
     {
         _templates = templates;
     }