fix(api): normalize payment currency codes

Author: chinook1001

apps/api/src/services/paymentService.js

@@ -3,7 +3,13 @@ export async function createPaymentIntent(payload) {
   return {
     paymentId: `pay_${Date.now()}`,
     amount: payload.amount,
-    currency: payload.currency ?? "usd",
+    currency: normalizeCurrency(payload.currency),
     provider: "stripe"
   };
 }
+
+function normalizeCurrency(currency) {
+  return typeof currency === "string" && currency.length > 0
+    ? currency.toUpperCase()
+    : "USD";
+}

apps/api/src/tests/paymentService.test.js

@@ -0,0 +1,15 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { createPaymentIntent } from "../services/paymentService.js";
+
+test("createPaymentIntent defaults to uppercase USD", async () => {
+  const intent = await createPaymentIntent({ amount: 2500 });
+
+  assert.equal(intent.currency, "USD");
+});
+
+test("createPaymentIntent normalizes lowercase currency codes", async () => {
+  const intent = await createPaymentIntent({ amount: 2500, currency: "eur" });
+
+  assert.equal(intent.currency, "EUR");
+});