Point production at the LAN MongoDB (192.168.1.7:27017)

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

.gitea/workflows/deploy.yml

@@ -50,6 +50,6 @@ jobs:
             echo "${{ secrets.REGISTRY_PASSWORD }}" | docker login git.aranroig.com -u "${{ secrets.REGISTRY_USER }}" --password-stdin
             cd /var/www/app/
             docker compose pull
-            docker compose up -d
+            docker compose up -d --remove-orphans
           EOF