Make a Dockerfile Pass the Linter

Labs have no container engine, so nothing is built or started: your files are checked by reading them, the way a reviewer or a CI linter would. docker-compose config (to validate Compose files) and hadolint (a Dockerfile linter) are installed.

CI now runs hadolint --ignore DL3008 --failure-threshold warning Dockerfile (pinning apt package versions, DL3008, is not required yet). The Dockerfile in /home/student/projects/chat-relay fails it.

Task

• Make that exact command pass on /home/student/projects/chat-relay/Dockerfile.
• The image must still be based on Ubuntu 24.04 (a pinned tag, not latest), install curl, ca-certificates and python3, copy app.py into /opt/chat-relay, and start python3 /opt/chat-relay/app.py.