refactor: modularize email processing logic and improve service structure

- Extract email template handling, rendering, and sending code into `Worker.Services` project.
- Introduce `EmailTemplateService`, `EmailTemplateRenderingService`, and `SendEmailService`.
- Simplify consumer logic by delegating to scoped services.
- Update project dependencies and package references accordingly.

HrynCo.NotificationService.Worker.Services/EmailProcessing/IEmailTemplateRenderingService.cs

@@ -0,0 +1,9 @@
+using HrynCo.NotificationService.Contracts.Messages;
+using HrynCo.NotificationService.DAL.Abstract.Templates;
+
+namespace HrynCo.NotificationService.Worker.Services.EmailProcessing;
+
+public interface IEmailTemplateRenderingService
+{
+    RenderedEmail Render(EmailTemplate template, SendEmailMessageData data);
+}