style: align hero image to top with object-position

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

site/assets/css/style.css

@@ -808,6 +808,7 @@ section[id] {
   position: relative;
   z-index: 0;
   background: var(--fitme-surface-2);
+  object-position: top;
 }
 
 /* Graceful fallback when image src is empty or 404 */