Add dummy default export for Vercel

cgen-2308aa3d76764e9dbe2a3d9f632788c6

api/opportunities.ts

@@ -313,3 +313,11 @@ export async function closeOpportunity(opportunityId: string, userId: string) {
     );
   }
 }
+
+// Dummy default export for Vercel (this file is a utility, not a handler)
+export default async function handler(
+  req: VercelRequest,
+  res: VercelResponse,
+) {
+  return res.status(501).json({ error: "Not a handler" });
+}