Configure server to serve frontend static files

backend/server.js

@@ -21,6 +21,14 @@ app.get('/api/health', (req, res) => {
   res.json({ status: 'OK', message: 'PubMed AI Explorer API is running' });
 });
 
+// Serve static files from the React app build directory
+app.use(express.static(path.join(__dirname, '../frontend/dist')));
+
+// Catch all handler: send back React's index.html file for any non-API routes
+app.get('*', (req, res) => {
+  res.sendFile(path.join(__dirname, '../frontend/dist/index.html'));
+});
+
 app.listen(PORT, () => {
   console.log(`Server running on port ${PORT}`);
 });