feat(SEO, Sitemap, Routing): enhance SEO and sitemap for new features

- Updated update-sitemap.sh to include new URLs for Vereinssoftware, Mitgliederverwaltung, Trainingsplanung, and Turniersoftware with appropriate lastmod dates and change frequencies.
- Enhanced server.js and seo.js with SEO configurations for the new pages, ensuring proper indexing and descriptions.
- Added new routes in router.js for the additional features, improving navigation and user access.
- Updated Home.vue to include links to the new features, enhancing user engagement and visibility.

frontend/public/sitemap.xml

@@ -15,6 +15,30 @@
     <changefreq>yearly</changefreq>
     <priority>0.3</priority>
   </url>
+  <url>
+    <loc>https://tt-tagebuch.de/vereinssoftware-tischtennis</loc>
+    <lastmod>2026-03-27</lastmod>
+    <changefreq>monthly</changefreq>
+    <priority>0.8</priority>
+  </url>
+  <url>
+    <loc>https://tt-tagebuch.de/mitgliederverwaltung-verein</loc>
+    <lastmod>2026-03-27</lastmod>
+    <changefreq>monthly</changefreq>
+    <priority>0.8</priority>
+  </url>
+  <url>
+    <loc>https://tt-tagebuch.de/trainingsplanung-tischtennis</loc>
+    <lastmod>2026-03-27</lastmod>
+    <changefreq>monthly</changefreq>
+    <priority>0.8</priority>
+  </url>
+  <url>
+    <loc>https://tt-tagebuch.de/turniersoftware-tischtennis</loc>
+    <lastmod>2026-03-27</lastmod>
+    <changefreq>monthly</changefreq>
+    <priority>0.8</priority>
+  </url>
   <url>
     <loc>https://tt-tagebuch.de/datenschutz</loc>
     <lastmod>2026-03-27</lastmod>