Send a synthetic success ping

Session-only console convenience — proves the ping pipeline works end to end before the monitored job is wired up. Enqueues a synthetic success ping through the exact same path a real ping takes; the response returns before the ping has necessarily been processed, so last_ping_at on GET /api/v1/checks/{id} may take a moment to update.

On a monitor that is currently down, this success ping resolves the open incident and sends a recovery alert to every attached destination, exactly as a real ping would — it is not a no-op probe.

Session-authenticated only: an API-key request gets 403 SESSION_ONLY, never 404 — an API key scripting a fake success would let an agent silence its own monitor without ever running the job it guards. Being a write, it also requires the CSRF double-submit header: 403 CSRF_REQUIRED if X-CSRF-Token is missing or does not match the lp_csrf cookie.

Refused with 400 TEST_PING_NOT_SUPPORTED for an http monitor: its liveness comes from the server's own probe, not an inbound ping, so a synthetic success ping would assert nothing real.

Rate-limited to one test ping per check per 5 seconds — a repeat within the window gets 429 with Retry-After: 5, and the earlier call still stands (the retry is not accepted). 503 PING_QUEUE_UNAVAILABLE when the ping queue could not be reached at all.