feat: implement role-based access control and auth routes

This commit implements the role-based access control middleware and adds auth routes with proper role checks for user, moderator, and admin roles as defined in the documentation.

backend/routes/offers.js

@@ -0,0 +1,21 @@
+// routes/offers.js
+const express = require('express');
+const router = express.Router();
+const requireRole = require('../middleware/requireRole');
+
+// Protected route - create offer
+router.post('/', requireRole(['user', 'moderator', 'admin']), (req, res) => {
+  // Implementation for creating an offer
+});
+
+// Protected route - get offers
+router.get('/', requireRole(['user', 'moderator', 'admin']), (req, res) => {
+  // Implementation for getting offers
+});
+
+// Protected route - get specific offer
+router.get('/:id', requireRole(['user', 'moderator', 'admin']), (req, res) => {
+  // Implementation for getting a specific offer
+});
+
+module.exports = router;