Auto-Reload bei neuem Build: no-cache index.html, build-time Check, SW skip-waiting

backend/src/index.js

@@ -82,8 +82,30 @@ app.get('/sw.js', (_req, res) => {
   res.sendFile(path.join(PUBLIC, 'sw.js'));
 });
 
-app.use(express.static(PUBLIC));
-app.get('*', (_req, res) => res.sendFile(path.join(PUBLIC, 'index.html')));
+app.use(express.static(PUBLIC, {
+  setHeaders: (res, filePath) => {
+    // JS/CSS Assets haben Hash im Namen → lang cachen
+    if (filePath.match(/\.(js|css)$/) && !filePath.includes('sw.js')) {
+      res.setHeader('Cache-Control', 'public, max-age=31536000, immutable');
+    }
+  }
+}));
+
+// index.html nie cachen
+app.get('*', (_req, res) => {
+  res.setHeader('Cache-Control', 'no-store, no-cache, must-revalidate');
+  res.setHeader('Pragma', 'no-cache');
+  res.sendFile(path.join(PUBLIC, 'index.html'));
+});
+
+// Build-Zeit Endpoint – Frontend prüft ob es eine neue Version gibt
+app.get('/api/build-time', (_req, res) => {
+  res.setHeader('Cache-Control', 'no-store');
+  try {
+    const ver = require('fs').readFileSync(path.join(__dirname, '../version.txt'), 'utf8').trim();
+    res.json({ buildTime: ver });
+  } catch { res.json({ buildTime: 'unknown' }); }
+});
 
 app.listen(4000, () => console.log('🚀 Dicken Dock läuft auf Port 4000'));