Execute recoverable stale-listing suspensions

Executes the stale-listing recovery sweep. Eligible listings are moved atomically to status: "paused" and review_status: "suspended", with collateral refunds when applicable; the response includes suspended[] and a backwards-compatible empty delisted: []. These listings remain recoverable through re-review. The sweep does not reactivate listings, publish hidden listings, or permanently reject recoverable stale supply. When either independent custody freeze is active, the route returns the typed 503 before database or suspension, refund, notification, or audit work.