Public live-probe status (customer-visible components only)

No auth required. Returns a redacted snapshot of the live upstream probes that back the admin `source-health` endpoint: API, Polymarket data, Kalshi data, Hyperliquid data, Polygon RPC. Each row carries a coarse `operational | degraded | outage` state — no error messages, no ping latency, no internal infra (Redis / Postgres). Cached for 30s in-process (shared with `/v1/admin/source-health`).