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.

docker-compose.yml

@@ -55,6 +55,11 @@ services:
       ADMIN_PASSWORD: ${ADMIN_PASSWORD:-admin123}
       ADMIN_FULL_NAME: ${ADMIN_FULL_NAME:-Main administrator}
       ADMIN_EMAIL: ${ADMIN_EMAIL:-admin@polotsk-transit.local}
+      FCM_ENABLED: "${FCM_ENABLED:-false}"
+      FCM_TOPIC: "${FCM_TOPIC:-route_alerts}"
+      FCM_ANDROID_CHANNEL_ID: "${FCM_ANDROID_CHANNEL_ID:-route_alerts}"
+      FIREBASE_PROJECT_ID: "${FIREBASE_PROJECT_ID:-}"
+      GOOGLE_APPLICATION_CREDENTIALS: "${GOOGLE_APPLICATION_CREDENTIALS:-}"
     ports:
       - "3000:3000"
     depends_on: