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.

README.md

@@ -1 +1,17 @@
 # hrynco-notification-service
+
+## Notification worker flow
+
+```mermaid
+flowchart TD
+    A[Worker host starts] --> B[Load config and register services]
+    B --> C[Start SendEmailConsumer]
+    C --> D[Receive message from notification.send-email]
+    D --> E[Resolve SendEmailService]
+    E --> F[Pick channel and template]
+    F --> G[Render email content]
+    G --> H[Send via SMTP]
+    H --> I[Update usage counters]
+    I --> J[Optionally publish result to reply queue]
+    H -. failure .-> K[Log and rethrow]
+```