Adds a maker-checker-gated "return" command on cheque books that flags presented-and-dishonoured leaves as terminal RETURNED (distinct from STOP_PAYMENT/drawer-initiated and LOST/custody-failure), following the same reason/actor/timestamp pattern already used for lost/cancelled/used leaves on m_cheque_leaf. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>