feat(gif-mood): hide empty sections for participants without GIFs

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

src/components/gif-mood/GifMoodBoard.tsx

@@ -310,6 +310,9 @@ export function GifMoodBoard({
         const isHidden = userRatingEntry?.hidden ?? false;
         const showHidden = !isCurrentUser && isHidden;
 
+        // Skip participants who haven't added any GIFs yet (except current user)
+        if (!isCurrentUser && userItems.length === 0) return null;
+
         return (
           <section key={user.id}>
             {/* Section header */}