Implement request handling for 3D models in app.js

- Added middleware to prevent direct access to /models/ paths, directing users to use /api/models/ instead for optimized 3D models.
- Updated comments to clarify the purpose of the new middleware and its role in serving models through the API.

backend/app.js

@@ -80,7 +80,14 @@ app.use('/api/blog', blogRouter);
 app.use('/api/termine', termineRouter);
 
 // Serve frontend SPA for non-API routes to support history mode clean URLs
+// /models/* nicht statisch ausliefern – nur über /api/models (Proxy mit Komprimierung)
 const frontendDir = path.join(__dirname, '../frontend');
+app.use((req, res, next) => {
+  if (req.path.startsWith('/models/')) {
+    return res.status(404).send('Use /api/models/ for 3D models (optimized).');
+  }
+  next();
+});
 app.use(express.static(path.join(frontendDir, 'dist')));
 app.get(/^\/(?!api\/).*/, (req, res) => {
   res.sendFile(path.join(frontendDir, 'dist', 'index.html'));