Reduce spacing between article subtitle and main content

Adjusted the `mb-2` to `mb-0` on the `p` tag for the article excerpt in `client/src/pages/Article.tsx` to decrease the bottom margin.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 0fb68265-c270-4198-9584-3d9be9bddb41
Replit-Commit-Checkpoint-Type: full_checkpoint

client/src/pages/Article.tsx

@@ -185,7 +185,7 @@ export default function Article() {
           <header className="mb-10">
             <h1 className="text-4xl font-bold mb-6 text-gray-900 leading-tight" data-testid="text-article-title">{article.title}</h1>
             {article.excerpt && (
-              <p className="text-lg text-gray-600 mb-2 leading-relaxed" data-testid="text-article-excerpt">
+              <p className="text-lg text-gray-600 mb-0 leading-relaxed" data-testid="text-article-excerpt">
                 {article.excerpt}
               </p>
             )}