add env var

docker-compose.yml

@@ -8,7 +8,13 @@ services:
     volumes:
       - /var/run/docker.sock:/var/run/docker.sock
   frontend:
-    build: ./frontend
+    build:
+      context: ./frontend
+      args:
+        # The URL of the backend API.
+        # This is passed to the React application during the build process.
+        # If not set, the frontend will default to http://localhost:3001 in the frontend code.
+        - REACT_APP_BACKEND_URL
     ports:
       - "3000:3000"
     depends_on: