SEO polish: OG image, favicons, 404, article schema, image optimization

- Add branded 1200x630 og-default.jpg; article pages use their hero as
  og:image, others use the default
- Wire the existing (previously unlinked) favicon set into every page
- Add branded 404.html with root-absolute paths + noindex
- Emit Article + localized BreadcrumbList JSON-LD on all article pages
- Convert 74 heavy served photos to WebP (28MB -> 8.5MB, -70%), rewrite
  references, add loading=lazy/decoding=async to below-fold images and
  fetchpriority=high to heroes (protect LCP)
- Stop tracking images/original/ (458MB of unused source masters; kept on
  disk, gitignored) and ignore .playwright-mcp/

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

en/student-welcome-guide/renew-change-graduate/index.html

@@ -16,15 +16,22 @@
     <meta property="og:title" content="What happens after the first year? - MSOS">
     <meta property="og:description" content="Annual renewal, repeat and transfer rights, losing status, the post-study route, and leaving Slovenia are all connected.">
     <meta property="og:url" content="https://msosorg.com/en/student-welcome-guide/renew-change-graduate/">
-    <meta property="og:image" content="https://msosorg.com/images/1-logo.png">
+    <meta property="og:image" content="https://msosorg.com/images/og-default.jpg">
     <meta property="og:locale" content="en_GB">
     <meta property="og:locale:alternate" content="mk_MK">
     <meta property="og:locale:alternate" content="sl_SI">
     <meta name="twitter:card" content="summary_large_image">
     <meta name="twitter:title" content="What happens after the first year? - MSOS">
     <meta name="twitter:description" content="Annual renewal, repeat and transfer rights, losing status, the post-study route, and leaving Slovenia are all connected.">
-    <meta name="twitter:image" content="https://msosorg.com/images/1-logo.png">
+    <meta name="twitter:image" content="https://msosorg.com/images/og-default.jpg">
     <script type="application/ld+json">{"@context":"https://schema.org","@type":"Organization","name":"Macedonian Student Organisation in Slovenia","alternateName":"MSOS","url":"https://msosorg.com/en/","logo":"https://msosorg.com/images/1-logo.png","email":"info@msosorg.com","address":{"@type":"PostalAddress","streetAddress":"Masarykova cesta 24","postalCode":"1000","addressLocality":"Ljubljana","addressCountry":"SI"},"sameAs":["https://www.facebook.com/msos.org","https://www.instagram.com/msosorg_com","https://www.linkedin.com/company/msos-org","https://www.youtube.com/@msosorg"]}</script>
+    <script type="application/ld+json">{"@context":"https://schema.org","@type":"Article","headline":"What happens after the first year?","description":"Annual renewal, repeat and transfer rights, losing status, the post-study route, and leaving Slovenia are all connected.","image":"https://msosorg.com/images/og-default.jpg","inLanguage":"en","author":{"@type":"Organization","name":"Macedonian Student Organisation in Slovenia","url":"https://msosorg.com/en/"},"publisher":{"@type":"Organization","name":"Macedonian Student Organisation in Slovenia","logo":{"@type":"ImageObject","url":"https://msosorg.com/images/1-logo.png"}},"mainEntityOfPage":"https://msosorg.com/en/student-welcome-guide/renew-change-graduate/"}</script>
+    <script type="application/ld+json">{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://msosorg.com/en/"},{"@type":"ListItem","position":2,"name":"Student Welcome Guide","item":"https://msosorg.com/en/student-welcome-guide/"},{"@type":"ListItem","position":3,"name":"What happens after the first year?","item":"https://msosorg.com/en/student-welcome-guide/renew-change-graduate/"}]}</script>
+    <link rel="icon" type="image/png" href="/favicon-96x96.png" sizes="96x96">
+    <link rel="icon" type="image/svg+xml" href="/favicon.svg">
+    <link rel="shortcut icon" href="/favicon.ico">
+    <link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png">
+    <link rel="manifest" href="/site.webmanifest">
     <!-- SEO:END -->
     <!-- Google Fonts -->
     <link rel="preconnect" href="https://fonts.googleapis.com">
@@ -271,7 +278,7 @@
         <div class="footer-main">
             <div class="footer-info">
                 <div class="footer-logo">
-                    <img src="../../../images/13-whitelogo.png" alt="Macedonian Student Organisation in Slovenia Logo">
+                    <img loading="lazy" decoding="async" src="../../../images/13-whitelogo.png" alt="Macedonian Student Organisation in Slovenia Logo">
                 </div>
                 <p class="footer-legal-name">Društvo Makedonska Študentska Organizacija v Sloveniji za študentsko podporo in kulturno sodelovanje</p>
                 <p>