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/repository/point_payment_repository.go

@@ -44,6 +44,8 @@ type PointPaymentRepository interface {
 	TotalPaid(ctx context.Context, orderID uuid.UUID) (float64, error)
 	// PaidWithPoints sums the rupiah of the order's completed EnakPoint payments.
 	PaidWithPoints(ctx context.Context, orderID uuid.UUID) (float64, error)
+	// PointMethodID returns the organization's EnakPoint payment method.
+	PointMethodID(ctx context.Context, organizationID uuid.UUID) (uuid.UUID, error)
 	InsertPayment(ctx context.Context, payment *entities.Payment) error
 	// UpdateOrderAfterPayment stores what is left to pay and marks the order paid when
 	// nothing is.
@@ -176,3 +178,19 @@ func (r *pointPaymentRepository) UpdateOrderAfterPayment(ctx context.Context, or
 	}
 	return nil
 }
+
+func (r *pointPaymentRepository) PointMethodID(ctx context.Context, organizationID uuid.UUID) (uuid.UUID, error) {
+	var ids []string
+	err := DBFromContext(ctx, r.db).WithContext(ctx).
+		Table("payment_methods").
+		Where("organization_id = ? AND type = ?", organizationID, constants.PaymentMethodTypePoint).
+		Limit(1).
+		Pluck("id::text", &ids).Error
+	if err != nil {
+		return uuid.Nil, fmt.Errorf("failed to find the EnakPoint payment method: %w", err)
+	}
+	if len(ids) == 0 {
+		return uuid.Nil, fmt.Errorf("the organization has no EnakPoint payment method")
+	}
+	return uuid.Parse(ids[0])
+}