fix: use preview transform for home page video teasers

thumbnail (300x300 square) was double-cropping inside the wide h-48
container. preview (800px, aspect-ratio preserved) lets object-cover
do the only crop, matching the videos and model pages.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/frontend/src/routes/+page.svelte

@@ -134,7 +134,7 @@ const { data } = $props();
         >
           <div class="relative">
             <img
-              src={getAssetUrl(video.image, 'thumbnail')}
+              src={getAssetUrl(video.image, 'preview')}
               alt={video.title}
               class="w-full h-48 object-cover group-hover:scale-105 transition-transform duration-300"
             />