Add SRI integrity hashes for CDN scripts and replace md5 with xxh128 for cache keys

- Add integrity/crossorigin attributes to chart.js and html5-qrcode CDN scripts
- Replace md5() with hash('xxh128') for Meilisearch cache key generation (non-sensitive context)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

templates/scanner/index.html.twig

@@ -10,7 +10,7 @@
     <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent">
     <meta name="apple-mobile-web-app-title" content="Scanner">
     <link rel="apple-touch-icon" href="/logo.png">
-    <script src="https://cdn.jsdelivr.net/npm/html5-qrcode@2.3.8/html5-qrcode.min.js"></script>
+    <script src="https://cdn.jsdelivr.net/npm/html5-qrcode@2.3.8/html5-qrcode.min.js" integrity="sha384-c9d8RFSL+u3exBOJ4Yp3HUJXS4znl9f+z66d1y54ig+ea249SpqR+w1wyvXz/lk+" crossorigin="anonymous"></script>
     <style>
         *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
         body { font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif; background: #111827; color: #f9fafb; min-height: 100dvh; }