fix: Add backend proxy for GLB files to resolve CORS in ImageTo3DModal

backend/server.js

@@ -246,6 +246,22 @@ app.post('/api/users/deduct-credit', authenticate, async (req, res) => {
   }
 });
 
+// 9.5 Proxy for downloading GLB files to fix CORS issues in frontend viewers
+app.get('/api/proxy/glb', async (req, res) => {
+  const { url } = req.query;
+  if (!url) return res.status(400).json({ error: 'URL required' });
+  try {
+    const response = await axios.get(url, { responseType: 'stream' });
+    res.setHeader('Content-Type', 'model/gltf-binary');
+    // Add CORS headers for the frontend to easily fetch it
+    res.setHeader('Access-Control-Allow-Origin', '*');
+    response.data.pipe(res);
+  } catch (err) {
+    console.error('Proxy error:', err.message);
+    res.status(500).json({ error: 'Failed to proxy file' });
+  }
+});
+
 // 10. Upload file
 app.post('/api/upload', authenticate, upload.single('file'), (req, res) => {
   if (!req.file) return res.status(400).json({ error: 'No file uploaded' });