Implement session-based authentication and add logout functionality

Fix #15

routes/auth.js

@@ -8,10 +8,20 @@ router.post('/login', (req, res) => {
     const password = process.env.AUTH_PASSWORD;
 
     if (user && user.name === username && user.pass === password) {
+        req.session.user = user.name;
         res.status(200).send('Login successful');
     } else {
         res.status(401).send('Authentication required');
     }
 });
 
+router.post('/logout', (req, res) => {
+    req.session.destroy((err) => {
+        if (err) {
+            return res.status(500).send('Error logging out');
+        }
+        res.status(200).send('Logout successful');
+    });
+});
+
 module.exports = router;