- Add Host header to curl healthcheck when container_hostname is defined
- Use PRETIX_PRETIX_ALLOWED_HOSTS to fix Django 400 Bad Request during healthcheck
- Centralize PRETIX_HOSTNAME from container_hostname var
- Add Redis broker/result backend config for Celery
See: https://chatgpt.com/share/68b59c42-c0fc-800f-9bfb-f1137c59b3de