feat: i18n — translate all hardcoded Italian strings (nutrition, facts, kiosk, gemini, scanner, shopping)

- Added 106 new translation keys across all 3 languages (it/en/de):
  - nutrition.* (11 keys): card title, score labels, health/variety/fresh bars, source
  - facts.* (70 keys): screensaver facts — greetings, expiry, shopping, categories, tips
  - kiosk.* (12 keys): update check, install flow, exit/refresh button titles
  - update.* (2 keys): badge label and button
  - gemini.* (2 keys): chat button title, not-configured tooltip
  - dashboard.banner_explain_title/btn/analyzing (3 keys): anomaly explain button
  - add.history_badge_tip (1 key): history badge tooltip
  - shopping.smart_last_update, names_already_updated (2 keys)
  - appliances.empty (1 key)
  - scanner.save_new_btn (1 key)
- app.js: replaced all remaining hardcoded Italian strings with t() calls
- api/index.php: fixed Frutta/Früchte Bring! loop (Pass 2 genericQualifiers)
- index.html: asset version bumped to v=20260511b

index.html

@@ -11,7 +11,7 @@
     <title>EverShelf</title>
     <link rel="manifest" href="manifest.json">
     <link rel="icon" type="image/png" href="assets/img/logo/logo_icon.png">
-    <link rel="stylesheet" href="assets/css/style.css?v=20260511a">
+    <link rel="stylesheet" href="assets/css/style.css?v=20260511b">
     <!-- QuaggaJS for barcode scanning -->
     <script src="https://cdn.jsdelivr.net/npm/@ericblade/quagga2@1.8.4/dist/quagga.min.js"></script>
     <!-- @xenova/transformers: ES-module bootstrap that exposes a lazy category-classifier as window._categoryPipelinePromise -->
@@ -1469,6 +1469,6 @@
     </div>
 </div>
 
-<script src="assets/js/app.js?v=20260511a"></script>
+<script src="assets/js/app.js?v=20260511b"></script>
 </body>
 </html>