test(po-attachments): use node env so the 25 MB cap assertion works

src/app/api/v1/purchase-orders/[id]/attachments/upload/route.test.ts

@@ -1,3 +1,4 @@
+// @vitest-environment node
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import { NextRequest } from "next/server";