Enhance Ratgeber section with new routes and SEO metadata

- Expanded the KNOWN_SPA_ROUTES in index.js to include new Ratgeber paths for improved navigation.
- Added detailed SEO metadata for the new Ratgeber routes in routes-seo.js, enhancing search engine visibility and user engagement.
- Updated robots.txt to allow indexing of the new Ratgeber pages, ensuring they are discoverable by search engines.

These changes collectively improve the site's informational resources and enhance SEO performance for chat-related guidance.

server/index.js

@@ -174,7 +174,20 @@ setupBroadcast(io, __dirname);
 // SPA-Fallback muss nach allen anderen Routen stehen
 if (IS_PRODUCTION) {
   const distPath = join(__dirname, '../docroot/dist');
-  const KNOWN_SPA_ROUTES = new Set(['/', '/partners', '/feedback', '/faq', '/regeln', '/sicherheit', '/mockup-redesign']);
+  const KNOWN_SPA_ROUTES = new Set([
+    '/',
+    '/partners',
+    '/feedback',
+    '/faq',
+    '/regeln',
+    '/sicherheit',
+    '/ratgeber',
+    '/ratgeber/erste-nachricht',
+    '/ratgeber/profil-tipps',
+    '/ratgeber/sicher-chatten',
+    '/ratgeber/red-flags',
+    '/mockup-redesign'
+  ]);
   app.use(express.static(distPath));
   // Fallback für Vue Router (SPA) - muss am Ende stehen
   app.get('*', (req, res) => {