fix(orders): keep the customer a new order is created for

CreateOrderContractToModel never copied customer_id, so every order from
POST /orders was saved without a customer. Paying it then earned no
EnakPoint or EnakCoin (skipped as NO_CUSTOMER, which is not logged).

The customer must now belong to the order's organization, as
SetOrderCustomer already requires: it is who earns once the order is paid,
and orders.customer_id has no foreign key. A nil UUID means no customer.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/transformer/order_transformer.go

@@ -27,6 +27,7 @@ func CreateOrderContractToModel(req *contract.CreateOrderRequest) *models.Create
 	return &models.CreateOrderRequest{
 		OutletID:     req.OutletID,
 		UserID:       req.UserID,
+		CustomerID:   req.CustomerID,
 		TableID:      req.TableID,
 		TableNumber:  req.TableNumber,
 		OrderType:    constants.OrderType(req.OrderType),