Fix admin API to serve admin.html on root route

- Updated server.js to serve admin.html on GET /
- Fixed path to admin.html in Docker container
- Admin panel now accessible at http://<ip>:3000

backend/server.js

@@ -8,6 +8,12 @@ const PORT = process.env.PORT || 3000;
 const JWT_SECRET = process.env.JWT_SECRET || 'fallback-secret-key';
 const APPS_FILE = path.join(__dirname, 'data', 'apps.json');
 
+// Serve admin frontend
+const adminPath = path.join(__dirname, 'admin.html');
+app.get('/', (req, res) => {
+  res.sendFile(adminPath);
+});
+
 app.use(express.json());
 app.use((req, res, next) => {
   res.setHeader('Access-Control-Allow-Origin', '*');