create payment roadmap pr a

lib/trip-pricing.ts

@@ -0,0 +1,12 @@
+/**
+ * Pricing helpers untuk trip. Single source of truth — semua gate "trip gratis"
+ * harus lewat sini, jangan compare `price === 0` inline.
+ */
+
+export function isFreeTrip(trip: { price: number }): boolean {
+  return trip.price <= 0;
+}
+
+export function isPaidTrip(trip: { price: number }): boolean {
+  return !isFreeTrip(trip);
+}