feat: add broker portfolio import

backend/src/routes/portfolio.ts

@@ -0,0 +1,22 @@
+import { Router } from 'express';
+import { asyncHandler } from '../utils';
+import * as portfolioService from '../services/portfolio';
+
+const router = Router();
+
+router.post(
+  '/',
+  asyncHandler(async (req, res) => {
+    try {
+      res.status(201).json(await portfolioService.importPortfolio(req.body));
+    } catch (error) {
+      if (error instanceof Error && /Invalid|Duplicate|must be|required|numeric/.test(error.message)) {
+        res.status(422).json({ error: 'VALIDATION_ERROR', message: error.message });
+        return;
+      }
+      throw error;
+    }
+  }),
+);
+
+export default router;