Restore a cancelled order

Un-cancels a previously cancelled Order. The order returns to its pre-cancellation state — its items become live again, line-item payments and discounts persist, and any associated visits/bookings are re-activated. Permissions: requires the caller to have the cancel ability on the order (the same permission used to cancel in the first place).

Use case: cancellation-by-mistake, customer change of mind shortly after cancellation, or a billing system mis-cancel that needs to be undone before the customer notices. For long-cancelled orders use the OrderService directly — restore expects a recent cancellation.