Fix: JSON sanitize fuer Fragmente, bessere Anleitungen; Backend index.html Expires-Header

backend/src/index.js

@@ -88,6 +88,12 @@ app.use(express.static(PUBLIC, {
     if (filePath.match(/\.(js|css)$/) && !filePath.includes('sw.js')) {
       res.setHeader('Cache-Control', 'public, max-age=31536000, immutable');
     }
+    // index.html niemals cachen – auch nicht über express.static
+    if (filePath.endsWith('index.html')) {
+      res.setHeader('Cache-Control', 'no-store, no-cache, must-revalidate');
+      res.setHeader('Pragma', 'no-cache');
+      res.setHeader('Expires', '0');
+    }
   }
 }));
 
@@ -95,6 +101,7 @@ app.use(express.static(PUBLIC, {
 app.get('*', (_req, res) => {
   res.setHeader('Cache-Control', 'no-store, no-cache, must-revalidate');
   res.setHeader('Pragma', 'no-cache');
+  res.setHeader('Expires', '0');
   res.sendFile(path.join(PUBLIC, 'index.html'));
 });