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),

internal/transformer/order_transformer_test.go

@@ -32,6 +32,20 @@ func TestCreateOrderContractToModelCarriesWeight(t *testing.T) {
 	require.Equal(t, weight, *result.OrderItems[0].Weight)
 }
 
+func TestCreateOrderContractToModelCarriesCustomer(t *testing.T) {
+	customerID := uuid.New()
+
+	result := CreateOrderContractToModel(&contract.CreateOrderRequest{
+		OutletID:   uuid.New(),
+		UserID:     uuid.New(),
+		CustomerID: &customerID,
+		OrderItems: []contract.CreateOrderItemRequest{{ProductID: uuid.New(), Quantity: 1}},
+	})
+
+	require.NotNil(t, result.CustomerID, "the order's customer is who earns EnakPoint and EnakCoin")
+	require.Equal(t, customerID, *result.CustomerID)
+}
+
 func TestAddToOrderContractToModelCarriesWeight(t *testing.T) {
 	weight := 0.8