Replace dual-consumer priority WorkerPool with a single consumer per
worker process. WORKER_PLAN=paid|free selects the Kafka topic and
consumer group ID (dish-recognition-paid / dish-recognition-free).
docker-compose now runs worker-paid and worker-free as separate services
for independent scaling. Makefile dev target launches both workers locally.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>