Operator: mark a beta access request invited, declined, or new again

Operator console only: requires the web session of an address in the operator allowlist of this installation, sent from the application itself. Every other signed-in caller and every valid Bearer token receives 404 NOT_FOUND, whether or not this installation has an operator configured; a caller with no valid credential receives 401, as on every route. Recorded in the operator log. Bookkeeping only: Tre has no sign-in gate, so a status admits and refuses nobody. Moving between invited and declined needs a reopen first (409).