fix(andreknie.de): normalize SEO metadata and document structure

privat/CV/andreknie.de/src/pages/ArticleSingle.jsx

@@ -11,10 +11,10 @@ export default function ArticleSingle() {
 
   if (!post) {
     return (
-      <div className="page-container app-container" style={{ textAlign: 'center', paddingTop: '150px' }}>
+      <main className="page-container app-container" style={{ textAlign: 'center', paddingTop: '150px' }}>
         <h2>Artikel nicht gefunden</h2>
         <Link to="/artikel" className="primary-button" style={{ marginTop: '20px' }}>Zurück zur Übersicht</Link>
-      </div>
+      </main>
     )
   }
 
@@ -23,8 +23,10 @@ export default function ArticleSingle() {
     : ''
 
   return (
-    <div className="page-container article-single-page">
-      <SEOHead 
+    <main className="page-container article-single-page">
+      <SEOHead
+        url={`/artikel/${post.slug}`}
+        type="article"
         title={`${post.title} | Dr. André Knie`} 
         description={post.excerpt || post.title}
       />
@@ -48,6 +50,6 @@ export default function ArticleSingle() {
           />
         </article>
       </div>
-    </div>
+    </main>
   )
 }