add server root

Author: Gochad

docker-compose.yml

@@ -339,6 +339,7 @@ services:
       - GF_SECURITY_ADMIN_PASSWORD=${GF_SECURITY_ADMIN_PASSWORD}
       - VIRTUAL_HOST=${FRONTEND_HOSTNAME}
       - LETSENCRYPT_HOST=${FRONTEND_HOSTNAME}
+      - GF_SERVER_ROOT_URL=https://frege.ii.uj.edu.pl/grafana/
     env_file: []
 
   # === [Frontend] ===