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

frontend/src/main.jsx

@@ -2,6 +2,45 @@ import React from 'react'
 import ReactDOM from 'react-dom/client'
 import App from './App.jsx'
 
+// ── Service Worker registrieren + Auto-Reload bei neuem Build ─────────────────
+if ('serviceWorker' in navigator) {
+  navigator.serviceWorker.register('/sw.js').then(reg => {
+    // Wenn ein neuer SW wartet: sofort übernehmen lassen
+    const takeOver = () => {
+      if (reg.waiting) {
+        reg.waiting.postMessage('SKIP_WAITING');
+      }
+    };
+    reg.addEventListener('updatefound', () => {
+      const newWorker = reg.installing;
+      newWorker?.addEventListener('statechange', () => {
+        if (newWorker.state === 'installed' && navigator.serviceWorker.controller) {
+          takeOver();
+        }
+      });
+    });
+    // Wenn SW übernimmt → Seite neu laden
+    navigator.serviceWorker.addEventListener('controllerchange', () => {
+      window.location.reload();
+    });
+  });
+
+  // Beim Start: Build-Zeit prüfen und bei neuer Version neu laden
+  const STORED_KEY = 'dd_build_time';
+  fetch('/api/build-time', { cache: 'no-store' })
+    .then(r => r.json())
+    .then(({ buildTime }) => {
+      const stored = localStorage.getItem(STORED_KEY);
+      if (stored && stored !== buildTime) {
+        localStorage.setItem(STORED_KEY, buildTime);
+        window.location.reload();
+      } else {
+        localStorage.setItem(STORED_KEY, buildTime);
+      }
+    })
+    .catch(() => {}); // offline – kein reload
+}
+
 ReactDOM.createRoot(document.getElementById('root')).render(
   <React.StrictMode><App /></React.StrictMode>
 )