Get an order by id

Returns the full order detail scoped to the caller account: header (id, external order id, channel, status, currency, creation), resolved customer, shipping/billing addresses, items (with metadata), mirrored payments, totals, the resolved state machine (id/code/name/version + transitions of the pinned version), the fulfillment orders block, and a unified chronological timeline that merges order status events, fulfillment order status events and shipment tracking events (each shipment event carries the resolved carrier and tracking code). An order that does not exist, is soft-deleted, or belongs to another account returns 404.