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/EmailChannels/Send/SendEmailHandler.cs

@@ -1,6 +1,5 @@
 using System.Net;
 using System.Net.Mail;
-using HrynCo.DAL.Abstract;
 using HrynCo.NotificationService.DAL.Abstract.Providers;
 using HrynCo.NotificationService.DAL.Abstract.Repositories;
 using HrynCo.NotificationService.Services.Core;
@@ -17,10 +16,9 @@ internal sealed class SendEmailHandler
 
     public SendEmailHandler(
         IContextualSerilogLogger<SendEmailCommand> logger,
-        IUnitOfWork unitOfWork,
         IEmailChannelRepository channels,
         IEmailChannelUsageRepository usage)
-        : base(logger, unitOfWork)
+        : base(logger)
     {
         _channels = channels;
         _usage = usage;