feat(loyalty): pay own orders with EnakPoint from the app

Adds POST /customer/orders/:id/pay-with-points (docs/prd-point-coin.md F9,
PC-306) for the customer app and self-order. It uses the same payment path
as the cashier, approved by the customer's PIN instead of a code: the
session alone is not enough (K8), and a wrong PIN takes nothing and counts
toward the lock.

A customer can pay only their own order; any other order, and one that
does not exist, answer 404 alike, so the endpoint does not reveal other
customers' orders. The method is the organization's EnakPoint method, no
cashier is recorded, and settling the order triggers earning through the
same onOrderPaid hook as every other payment.

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

internal/service/customer_order_payment_service.go

@@ -0,0 +1,34 @@
+package service
+
+import (
+	"context"
+
+	"github.com/google/uuid"
+
+	"apskel-pos-be/internal/contract"
+	"apskel-pos-be/internal/models"
+	"apskel-pos-be/internal/processor"
+	"apskel-pos-be/internal/transformer"
+)
+
+// CustomerOrderPaymentService lets customers pay their own orders with EnakPoint in the
+// app or a self-order (docs/prd-point-coin.md F9).
+type CustomerOrderPaymentService interface {
+	PayWithPoints(ctx context.Context, customerID, orderID uuid.UUID, req *contract.PayWithPointsRequest, info models.CustomerPinRequestInfo) *contract.Response
+}
+
+type CustomerOrderPaymentServiceImpl struct {
+	orders processor.OrderProcessor
+}
+
+func NewCustomerOrderPaymentService(orders processor.OrderProcessor) *CustomerOrderPaymentServiceImpl {
+	return &CustomerOrderPaymentServiceImpl{orders: orders}
+}
+
+func (s *CustomerOrderPaymentServiceImpl) PayWithPoints(ctx context.Context, customerID, orderID uuid.UUID, req *contract.PayWithPointsRequest, info models.CustomerPinRequestInfo) *contract.Response {
+	payment, err := s.orders.PayWithPointsInApp(ctx, customerID, orderID, req.Points, req.Pin, info)
+	if err != nil {
+		return PointPaymentErrorResponse(err)
+	}
+	return contract.BuildSuccessResponse(transformer.PaymentModelToContract(payment))
+}