fix: production save errors and import HR dashboard data

Resolve invalid task creator IDs, fix API routing and file uploads on Vercel, and replace dummy seed data with HR_Dashboard import.

backend/src/app.ts

@@ -12,14 +12,20 @@ app.use(helmet());
 const allowedOrigins = [
   'http://localhost:3000',
   'http://172.16.8.248:3000',
+  'https://eene-dashboard.vercel.app',
   process.env.FRONTEND_URL,
 ].filter(Boolean) as string[];
 
+function isAllowedOrigin(origin: string): boolean {
+  if (allowedOrigins.includes(origin)) return true;
+  if (/^https:\/\/[\w-]+\.vercel\.app$/.test(origin)) return true;
+  return false;
+}
+
 app.use(
   cors({
     origin: (origin, callback) => {
-      // 같은 서버에서 직접 호출하거나 허용된 origin이면 통과
-      if (!origin || allowedOrigins.includes(origin)) {
+      if (!origin || isAllowedOrigin(origin)) {
         callback(null, true);
       } else {
         callback(new Error(`CORS 차단: ${origin}`));