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/NotificationBaseRepository.cs

@@ -0,0 +1,20 @@
+namespace HrynCo.NotificationService.DAL.EF.Core;
+
+using HrynCo.DAL.Abstract.Entities;
+using HrynCo.DAL.EF.Core;
+
+public abstract class NotificationBaseRepository<TEntity>
+    : BaseRepository<NotificationEfRepository<TEntity>, NotificationDbContext, TEntity, Guid> where TEntity : Entity
+{
+    protected NotificationBaseRepository(NotificationDbContext dbContext)
+    {
+        DbContext = dbContext;
+    }
+
+    private NotificationDbContext DbContext { get; set; }
+
+    protected override NotificationEfRepository<TEntity> CreateEfRepository()
+    {
+        return new NotificationEfRepository<TEntity>(DbContext);
+    }
+}