fix(blog): table of contents scroll links

Fixes an issue where TOC links wouldn't scroll due to

ID generation mismatches on MDX headers containing

formatted text or German umlauts.

lib/blog.ts

@@ -109,7 +109,12 @@ export async function getAllPostsMetadata(locale: string): Promise<Partial<PostM
 export async function getAdjacentPosts(
   slug: string,
   locale: string,
-): Promise<{ prev: PostMdx | null; next: PostMdx | null; isPrevRandom?: boolean; isNextRandom?: boolean }> {
+): Promise<{
+  prev: PostMdx | null;
+  next: PostMdx | null;
+  isPrevRandom?: boolean;
+  isNextRandom?: boolean;
+}> {
   const posts = await getAllPosts(locale);
   const currentIndex = posts.findIndex((post) => post.slug === slug);
 
@@ -127,7 +132,7 @@ export async function getAdjacentPosts(
   let isPrevRandom = false;
 
   const getRandomPost = (excludeSlugs: string[]) => {
-    const available = posts.filter(p => !excludeSlugs.includes(p.slug));
+    const available = posts.filter((p) => !excludeSlugs.includes(p.slug));
     if (available.length === 0) return null;
     return available[Math.floor(Math.random() * available.length)];
   };
@@ -154,17 +159,42 @@ export function getReadingTime(content: string): number {
   return Math.ceil(minutes);
 }
 
+export function generateHeadingId(text: string): string {
+  let id = text.toLowerCase();
+  id = id.replace(/ä/g, 'ae');
+  id = id.replace(/ö/g, 'oe');
+  id = id.replace(/ü/g, 'ue');
+  id = id.replace(/ß/g, 'ss');
+
+  id = id.replace(/[*_`]/g, '');
+  id = id.replace(/[^\w\s-]/g, '');
+  id = id
+    .replace(/\s+/g, '-')
+    .replace(/-+/g, '-')
+    .replace(/^-+|-+$/g, '');
+
+  return id || 'heading';
+}
+
+export function getTextContent(node: any): string {
+  if (typeof node === 'string') return node;
+  if (typeof node === 'number') return node.toString();
+  if (Array.isArray(node)) return node.map(getTextContent).join('');
+  if (node && typeof node === 'object' && node.props && node.props.children) {
+    return getTextContent(node.props.children);
+  }
+  return '';
+}
+
 export function getHeadings(content: string): { id: string; text: string; level: number }[] {
   const headingLines = content.split('\n').filter((line) => line.match(/^#{2,3}\s/));
 
   return headingLines.map((line) => {
     const level = line.match(/^#+/)?.[0].length || 0;
-    const text = line.replace(/^#+\s/, '').trim();
-    const id = text
-      .toLowerCase()
-      .replace(/[^\w\s-]/g, '')
-      .replace(/\s+/g, '-');
+    const rawText = line.replace(/^#+\s/, '').trim();
+    const cleanText = rawText.replace(/[*_`]/g, '');
+    const id = generateHeadingId(cleanText);
 
-    return { id, text, level };
+    return { id, text: cleanText, level };
   });
 }