fix: API_URL env for server-side fetches

deploy/docker-compose.yml

@@ -39,6 +39,8 @@ services:
       args:
         NEXT_PUBLIC_API_URL: https://codetutor-demo.kschappell.com
     container_name: codetutor-frontend
+    environment:
+      API_URL: http://backend:8000
     depends_on:
       - backend
     restart: unless-stopped