add toggle for allowing registrations from the frontend

backend/routes/users.js

@@ -6,6 +6,14 @@ const User = require('../models/User');
 // Register new user
 router.post('/register', async (req, res) => {
   try {
+    // Check if registration is enabled
+    const registrationEnabled = process.env.ALLOW_REGISTRATION !== 'false';
+    if (!registrationEnabled) {
+      return res.status(403).json({ 
+        error: 'Registration is currently disabled' 
+      });
+    }
+
     const { username, email, password } = req.body;
     
     // Check if user already exists