Structured logging via JsonFormatter replaces uvicorn's default format so
Loki can parse timestamps and fields. 14 business metrics (scrape stats,
throttle events, circuit breaker state, cache hit rate, OCR success rate,
Celery task lifecycle) are defined in a shared metrics module and
instrumented across the scraper pipeline, API, and workers. Celery
workers expose a Prometheus HTTP endpoint on configurable ports.
Per-user rate limits via Redis sliding window, IP-restricted /metrics
endpoint, audit logging of all requests, CORS tightening, and export
caps on listing/geojson endpoints.
