fix(andreknie.de): close SEO review gaps

privat/CV/andreknie.de/src/components/SEOHead.jsx

@@ -1,4 +1,4 @@
-import React from 'react'
+import React, { useEffect } from 'react'
 import { Helmet } from 'react-helmet-async'
 import { absoluteUrl, BRAND_SUFFIX, DEFAULT_DESCRIPTION, DEFAULT_IMAGE, DEFAULT_TITLE, normalizeTitle } from './seo.js'
 
@@ -9,6 +9,10 @@ export default function SEOHead({ title, description, url, image, type = 'websit
   const canonicalUrl = absoluteUrl(url || '/', '/')
   const imageUrl = absoluteUrl(image, DEFAULT_IMAGE)
 
+  useEffect(() => {
+    document.head.querySelectorAll('[data-seo-fallback]').forEach(node => node.remove())
+  }, [])
+
   return (
     <Helmet>
       <title>{siteTitle}</title>

privat/CV/andreknie.de/src/components/SEOHead.test.jsx

@@ -25,6 +25,25 @@ describe('SEOHead', () => {
     expect(document.head.querySelector('link[rel="canonical"]')?.getAttribute('href')).toBe('https://andreknie.de/artikel')
   })
 
+  it('replaces static fallback metadata instead of duplicating it', () => {
+    document.head.insertAdjacentHTML('beforeend', `
+      <title data-seo-fallback>Fallback</title>
+      <meta data-seo-fallback name="description" content="Fallback description">
+      <link data-seo-fallback rel="canonical" href="https://andreknie.de/">
+    `)
+
+    render(
+      <HelmetProvider>
+        <SEOHead title="Artikel" description="Article description" url="/artikel" />
+      </HelmetProvider>,
+    )
+
+    expect(document.head.querySelectorAll('[data-seo-fallback]')).toHaveLength(0)
+    expect(document.head.querySelectorAll('title')).toHaveLength(1)
+    expect(document.head.querySelectorAll('meta[name="description"]')).toHaveLength(1)
+    expect(document.head.querySelectorAll('link[rel="canonical"]')).toHaveLength(1)
+  })
+
   it('normalizes relative and absolute image URLs', () => {
     const { rerender } = render(
       <HelmetProvider>