services:
  spa-app:
    environment:
      - CLIENT_BASE_PATH=
      - CLIENT_API_URL=https://
      - CLIENT_APP_NAME=
      - CLIENT_DEBUG=
      - CLIENT_MAP_TILE_ENDPOINT=https://
      - CLIENT_MAP_TILE_API_KEY=
networks:
  traefik:             # ← key stays literal, no variables here
    external: true     # shorthand; Compose will look for a network literally named “traefik”