Health Check

Health check endpoint.

Probes the three critical subsystems — database, object storage, and the headless browser — and returns 503 if any is unhealthy so a load balancer drains/restarts the node. The browser check is a read-only CDP round-trip (BrowserManager.is_browser_healthy) that never triggers recovery, and the response carries saturation stats (in-use slots, queue depth, crash recoveries) for observability. The blocking DB/storage probes run off the event loop via to_thread so the async handler never stalls.