feat: implement role-based access control and auth routes

This commit implements the role-based access control middleware and authentication routes as per the project's requirements. It includes:

backend/app.js

@@ -0,0 +1,35 @@
+const express = require('express');
+const cors = require('cors');
+const helmet = require('helmet');
+const db = require('./db');
+const authRoutes = require('./routes/auth');
+const rolesRoutes = require('./routes/roles');
+
+const app = express();
+
+// Middleware
+app.use(helmet());
+app.use(cors());
+app.use(express.json());
+
+// Routes
+app.use('/auth', authRoutes);
+app.use('/roles', rolesRoutes);
+
+// Health check endpoint
+app.get('/health', (req, res) => {
+  res.json({ status: 'OK', timestamp: new Date().toISOString() });
+});
+
+// Error handling middleware
+app.use((err, req, res, next) => {
+  console.error(err.stack);
+  res.status(500).json({ error: 'Something went wrong!' });
+});
+
+// 404 handler
+app.use('*', (req, res) => {
+  res.status(404).json({ error: 'Route not found' });
+});
+
+module.exports = app;