Liveness, and the platform healthcheck target.

Exempt from the global default limit. The limiter keys on request.client.host, which behind a platform proxy is one bucket for every caller, so an unrelated burst of traffic would 429 the healthcheck and get a healthy process restarted. A limit whose failure mode is worse than the traffic it throttles protects nothing — and this route reads no database and does no work. Undecorated public reads keep the default.