feat: Implement alert creation service with FCM notifications

- Add AlertCreationService to handle alert creation and notifications.
- Implement idempotency key support to prevent duplicate alerts.
- Create alert notification service for sending FCM messages.
- Add tests for alert creation and notification services.
- Document FCM notification flow and alert creation process.

backend/Dockerfile

@@ -1,4 +1,4 @@
-FROM node:18-alpine
+FROM node:22-alpine
 
 WORKDIR /app