fix: revert API_URL to use backend service name in docker-compose

Author: siiddhantt

deployment/docker-compose.yaml

@@ -45,7 +45,7 @@ services:
       - CELERY_BROKER_URL=redis://redis:6379/0
       - CELERY_RESULT_BACKEND=redis://redis:6379/1
       - MONGO_URI=mongodb://mongo:27017/docsgpt
-      - API_URL=http://host.docker.internal:7091
+      - API_URL=http://backend:7091
       - CACHE_REDIS_URL=redis://redis:6379/2
     volumes:
       - ../application/indexes:/app/indexes