feat(seo, routing): add Bisaya learning and German for Bisaya courses

- Introduced new routes for Bisaya learning and German for Bisaya courses, enhancing the marketing section of the application.
- Updated sitemap.xml to include new course URLs for better SEO visibility.
- Added localization entries for both courses in English and German, improving content accessibility for users.
- Enhanced SEO metadata generation for the new courses, ensuring proper indexing and visibility in search engines.
- Updated VocabLandingView to feature links to the new courses, improving user navigation and engagement.

frontend/public/sitemap.xml

@@ -15,6 +15,16 @@
     <changefreq>weekly</changefreq>
     <priority>0.8</priority>
   </url>
+  <url>
+    <loc>https://www.your-part.de/bisaya-lernen</loc>
+    <changefreq>weekly</changefreq>
+    <priority>0.8</priority>
+  </url>
+  <url>
+    <loc>https://www.your-part.de/deutsch-fuer-bisaya</loc>
+    <changefreq>weekly</changefreq>
+    <priority>0.8</priority>
+  </url>
   <url>
     <loc>https://www.your-part.de/falukant</loc>
     <changefreq>weekly</changefreq>