Motor de canje: dado el snapshot del checkout (POS, web QR o kiosko), valida que se cumplen los requisitos de la recompensa (compra mínima, tipo de pedido, producto en carrito, combinaciones, límites...) ANTES de canjearla. No produce efectos secundarios.

Integration access is restricted to the credential's location. Pagination, monetary units and response envelopes are endpoint-specific; use the schema below. Do not assume that POST/PATCH requests are safe to retry after a timeout.