use image in compose instead of building one

docker-compose.yaml

@@ -5,6 +5,7 @@ services:
     container_name: backend
     build:
       context: ./backend
+    image: metagenedb-backend
     volumes:
       - ./backend:/code
       - django-static:/backend/public/static
@@ -73,13 +74,13 @@ services:
 
   celery:
     container_name: celery
-    build:
-      context: ./backend
+    image: metagenedb-backend
     volumes:
       - ./backend:/code
     depends_on:
       - postgresql
       - redis
+      - backend
     command: bash -c 'manage.py watch_celery'
     networks:
       - main