refactor: backend port 8000 → 7000 pour eviter conflits applicatifs

- Dockerfile: EXPOSE + CMD uvicorn --port 7000
- app/config.py: PORT default 8000 → 7000
- nginx default.conf: 6x proxy_pass backend:8000 → backend:7000
- docker-compose.prod.yml: BACKEND_PORT default 8001 → 7000, internal 7000
- docker-compose.yml (dev): 8000:8000 → 7000:7000
- imago-admin/docker-compose.yml: VITE_API_BASE_URL + port mapping → 7000
- .env.example: BACKEND_PORT=8001 → 7000
- deploy.sh: defaults + invites port 8001 → 7000

docker-compose/docker-compose.prod.yml

@@ -15,7 +15,7 @@ services:
     image: docker-registry.dev.home:5000/imago-backend:latest
     user: "1000:1000"
     ports:
-      - "${BACKEND_PORT:-8001}:8000"
+      - "${BACKEND_PORT:-7000}:7000"
     env_file:
       - .env
     environment: