Approve Family Review

Guardian approves the Moment.

Round-4 atomic promotion: the Moment was created with audience='only_me' + intended_audience=<requested>. On the FIRST successful approval (any guardian), we promote:

UPDATE moments
SET audience = intended_audience,
    circle_ids = COALESCE(intended_circle_ids, circle_ids),
    intended_audience   = NULL,
    intended_circle_ids = NULL,
    updated_at = now()
WHERE id = :mid
  AND audience = 'only_me'
  AND intended_audience IS NOT NULL

The WHERE clause is the belt-and-suspenders: if anything has tampered with the row (audience already promoted, intent already cleared), the UPDATE is a no-op and the second guardian's approval is idempotent.