content: add real photos + captions to all Student Welcome Guide pages

Replace the "Image placeholder" boxes on all 30 guide subpages + the guide
landing hero with real, optimized photos and captions, EN/MK/SI (93 figures).

- 31 source photos (up to 18 MB) optimized to WebP (<=1400px, all <500 KB)
  as images/guide-<slug>.webp.
- Captions follow the Get-to-Know style: description + "Photo:/Фото:/Foto:"
  + linked source (or MSOS for own event photos). Photographer credits kept.
  MK/SI descriptions are translated (proofread welcome).
- CSS: move the banner crop from the figure onto the <img> so the caption
  shows below it (was clipped by the figure's fixed height + overflow).

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

si/student-welcome-guide/student-transport/index.html

@@ -198,8 +198,9 @@
                 <h1>Subvencioniran javni prevoz za študente</h1>
                 <p class="article-subtitle">Nacionalne vozovnice IJPP, mestni prevoz in izposoja koles. Upravičenost ni odvisna od razdalje do fakultete.</p>
             </header>
-            <figure class="guide-hero-image guide-hero-image--placeholder">
-                <span><i class="fas fa-image" aria-hidden="true"></i>Mesto za sliko</span>
+            <figure class="guide-hero-image">
+                <img width="1400" height="1050" fetchpriority="high" decoding="async" src="../../../images/guide-student-transport.webp" alt="Mestni avtobus v Mariboru.">
+                <figcaption>Mestni avtobus v Mariboru. Foto: <a href="https://sl.wikipedia.org/wiki/Mestna_avtobusna_linija_%C5%A1t._6_%28Maribor%29" target="_blank" rel="noopener">wikipedia.org</a></figcaption>
             </figure>
 
             <div class="article-body">