refactor backend and persist stock campaign queue

backend/routes/stockRoutes.js

@@ -0,0 +1,26 @@
+const express = require('express');
+const { authenticateAPIKey, verifyToken } = require('../auth');
+const { listStock, upsertStockItems } = require('../services/stockService');
+
+const router = express.Router();
+
+router.get('/stock', verifyToken, async (req, res) => {
+    try {
+        res.json(await listStock());
+    } catch (error) {
+        console.error('Error fetching stock:', error);
+        res.status(500).json({ error: 'Internal Server Error' });
+    }
+});
+
+router.post('/stock', authenticateAPIKey, async (req, res) => {
+    res.status(201).json({ message: 'Stock data received, processing in background' });
+
+    const payload = Array.isArray(req.body) ? req.body : [req.body];
+
+    upsertStockItems(payload).catch((error) => {
+        console.error('Database stock insert error:', error);
+    });
+});
+
+module.exports = router;