Production uses the network's database server instead of a mongo service
inside the stack (the compose-managed one never served the API). Dev is
unchanged: backend/.env keeps localhost:27017.
- docker-compose.yml: MONGO_URI=mongodb://192.168.1.7:27017/mathew; drop
the in-stack mongo service, its volume and the healthcheck gate
- deploy.yml: up -d --remove-orphans so yesterday's mongo container is
retired when the new compose lands