fix(scoring): PWA installierbar + Mikrofon auf Android/Chrome

Web-App-Manifest, Service Worker und Icons für Install-Prompt;
Permissions-Policy erlaubt Mikrofon (self); getUserMedia vor Speech API.

Co-authored-by: Cursor <cursoragent@cursor.com>

public/scoring/sw.js

@@ -0,0 +1,29 @@
+const CACHE = 'scoring-v1';
+const ASSETS = [
+  './',
+  './index.html',
+  './manifest.webmanifest',
+  './icons/icon-192.png',
+  './icons/icon-512.png'
+];
+
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(CACHE).then((cache) => cache.addAll(ASSETS)).then(() => self.skipWaiting())
+  );
+});
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys()
+      .then((keys) => Promise.all(keys.filter((k) => k !== CACHE).map((k) => caches.delete(k))))
+      .then(() => self.clients.claim())
+  );
+});
+
+self.addEventListener('fetch', (event) => {
+  if (event.request.method !== 'GET') return;
+  event.respondWith(
+    caches.match(event.request).then((cached) => cached || fetch(event.request))
+  );
+});