ui(article): editorial standard — cap featured image at 480px (mirror of BB)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/articles/[slug]/ArticleDetailClient.tsx

@@ -341,17 +341,17 @@ export default function ArticleDetailClient({ article, relatedArticles, relatedF
               </div>
             </div>
 
-            {/* Featured Image */}
-            <div className="mb-8 overflow-hidden rounded-sm">
+            {/* Featured Image — editorial standard: cap at 480px high. */}
+            <figure className="mb-8 overflow-hidden rounded-sm bg-[#F1F5F9] flex items-center justify-center" style={{maxHeight: 480}}>
               <AppImage
                 src={article.image}
                 alt={article.alt}
                 width={800}
                 height={450}
-                className="w-full h-auto object-cover"
+                className="max-h-[480px] w-auto max-w-full object-contain"
                 priority
               />
-            </div>
+            </figure>
 
             {/* Article Body */}
             {/* DO NOT OVERRIDE — article body prose styles */}