feat: add gateway-neutral payment package

packages/payment/src/runtime-webhook.ts

@@ -0,0 +1,7 @@
+import { getPaymentService } from "./core.ts";
+
+export async function POST(ctx: { req: Request; params?: Record<string, string> }) {
+  const gateway = ctx.params?.gateway?.trim();
+  if (!gateway) return Response.json({ error: "payment gateway is required" }, { status: 400 });
+  return getPaymentService().paymentWebhookHandler(gateway)(ctx);
+}