fix: add certbot volume mount for HTTPS certificates

Nginx now properly mounts the Let's Encrypt certificates to serve HTTPS.

Job ID: MTAD-IMPL-2025-11-18-CL

backend/docker-compose.yml

@@ -99,6 +99,7 @@ services:
       - "443:443"
     volumes:
       - ./nginx.conf:/etc/nginx/nginx.conf:ro
+      - ./certbot/conf:/etc/letsencrypt:ro
       - ../web/out:/usr/share/nginx/html:ro
     networks:
       - mtad-network