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.DAL.EF/Core/NotificationEfRepository.cs

@@ -0,0 +1,13 @@
+namespace HrynCo.NotificationService.DAL.EF.Core;
+
+using HrynCo.DAL.Abstract.Entities;
+using HrynCo.DAL.EF.Core;
+
+public class NotificationEfRepository<TEntity> : BaseEfRepository<NotificationDbContext, TEntity, Guid>
+    where TEntity : class, IEntity<Guid>
+{
+    public NotificationEfRepository(NotificationDbContext dbContext) :
+        base(dbContext)
+    {
+    }
+}