Turn the monitor's free status page on or off (issue

Owner role only — publishing a public URL is an owner decision, the same gate as /account/feed-token. Repeating {"enabled":true} on an already-on page returns the same URL. {"enabled":false} revokes the URL immediately at the origin (a caching CDN in front of the status host may still serve the old page for up to 60 seconds — see STATUS_PAGE_URL/Free Status Page in SPEC.md). Turning it back on mints a different token. The body must be exactly {"enabled": <bool>} — a missing or null enabled, a non-boolean value, or any other key is 400 and leaves the stored token unchanged.