fix: format PostCard date with toLocaleDateString

- Replace raw {date} with toLocaleDateString formatting
- Matches post detail page date formatting

components/blog/PostCard.tsx

@@ -25,7 +25,7 @@ export function PostCard({ slug, title, date, excerpt, tags = [], author, readin
           </div>
         )}
         <div className="flex items-center gap-3 text-xs text-ink-soft mb-3">
-          <time className="font-mono">{date}</time>
+          <time className="font-mono">{new Date(date).toLocaleDateString('en-US', { year: 'numeric', month: 'short', day: 'numeric' })}</time>
           {author && <span className="text-ink-soft/70">·</span>}
           {author && <span>{author}</span>}
           {readingTime && <span className="text-ink-soft/70">·</span>}