-- Prober availability indication (see docs/USAGE.md, "Управление
-- площадками"): sites gain the same hostname/state/heartbeat tracking
-- validators already have, so the dashboard can show whether a prober is
-- actually connected and polling.

ALTER TABLE sites ADD COLUMN hostname          TEXT NOT NULL DEFAULT '';
ALTER TABLE sites ADD COLUMN state             TEXT NOT NULL DEFAULT 'unregistered';
ALTER TABLE sites ADD COLUMN last_heartbeat_at TIMESTAMP;