feat(seo): add Google Preferred Sources button + footer link

New self-contained preferred-source.js (referenced site-wide via
seo_inject GA_LINES):
- small "Add us on Google" text link in the footer (.legal-links) on
  every page, trilingual, using the domain deeplink;
- Google's official interactive pill (publisher.js) on the homepage,
  News hub and Blog hub only, localized (en/mk/sl).
Lets readers mark MSOS as a preferred source (Top Stories / Discover /
News / AI surfaces). Cache-bust bump included.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

404.html

@@ -25,7 +25,7 @@
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
     <link href="https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap" rel="stylesheet">
     <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.5.1/css/all.min.css" crossorigin="anonymous" referrerpolicy="no-referrer">
-    <link rel="stylesheet" href="/css/main.css?v=a90a6258">
+    <link rel="stylesheet" href="/css/main.css?v=cd97d474">
 
     <link rel="icon" type="image/png" href="/favicon-96x96.png" sizes="96x96">
     <link rel="icon" type="image/svg+xml" href="/favicon.svg">
@@ -70,7 +70,7 @@
             </p>
         </div>
     </main>
-<link rel="stylesheet" href="/assistant.css?v=a90a6258">
-<script src="/assistant.js?v=a90a6258" defer></script>
+<link rel="stylesheet" href="/assistant.css?v=cd97d474">
+<script src="/assistant.js?v=cd97d474" defer></script>
 </body>
 </html>