Set Ai Opt Out

Stop the AI support responder for one person. Body: {request_id | user_id | address, reason}. From an item (request_id, the desk action) the person is the row's account (user id) AND its requester address (the sender of an e-mail item — flagged even when unverified: hiding more only means a human reads it — or the account / notifier address). Idempotent: the same person already covered returns the existing opt-out (200).