chore(docker): add OpenAI config to flow-engine

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker-compose.yml

@@ -92,6 +92,8 @@ services:
       REDIS_URL: redis://redis:6379
       API_GATEWAY_URL: http://api-gateway:8000
       WHATSAPP_CORE_URL: http://whatsapp-core:3001
+      OPENAI_API_KEY: ${OPENAI_API_KEY:-}
+      OPENAI_MODEL: ${OPENAI_MODEL:-gpt-4o-mini}
     depends_on:
       postgres:
         condition: service_healthy