chore: pass ARTEX_UNTRUSTED_BOUNDARY to the artex service

Without this line the toggle set in .env never reached the container under
docker compose. The default is empty, which keeps the boundary off.

docker-compose.yml

@@ -36,6 +36,7 @@ services:
       ARTEX_LLM_PROXY: ${ARTEX_LLM_PROXY:-}
       ARTEX_JWT_KEY_DIR: /app/keys
       ARTEX_TRUSTED_PROXIES: ${ARTEX_TRUSTED_PROXIES:-}
+      ARTEX_UNTRUSTED_BOUNDARY: ${ARTEX_UNTRUSTED_BOUNDARY:-}
     ports:
       - "${ARTEX_BIND_ADDR:-127.0.0.1}:8787:8787"
       - "127.0.0.1:8788:8788"