Fix: Replace ES2018 regex flag with compatible pattern

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/lib/blog.ts

@@ -88,7 +88,7 @@ function parseMarkdownPost(filename: string, content: string): BlogPost | null {
     // Extract excerpt from introduction or meta description
     let excerpt = metaDescription;
     if (!excerpt) {
-      const introMatch = content.match(/## Einführung\s*\n\n(.+?)(?:\n\n|$)/s);
+      const introMatch = content.match(/## Einführung\s*\n\n([\s\S]+?)(?:\n\n|$)/);
       if (introMatch) {
         excerpt = introMatch[1].trim().slice(0, 200) + '...';
       }