Enhance SEO and URL handling in router and server

- Updated the router to ensure canonical URLs are correctly formatted, particularly for the home path.
- Added middleware in the server to remove tracking/session query parameters, preventing duplicate URLs from being indexed by Google.
- Set canonical link headers in SEO routes to assist search engines in URL attribution.

These changes improve SEO performance and ensure cleaner URL structures across the application.

client/src/router/index.js

@@ -243,7 +243,9 @@ function updateJsonLd(schema) {
 
 router.beforeEach((to, from, next) => {
   const meta = to.meta || {};
-  const pageUrl = `${SITE_URL}${to.path}`;
+  // Immer eine eindeutige kanonische URL (Home explizit mit / am Ende der Origin)
+  const path = to.path === '' ? '/' : to.path;
+  const pageUrl = path === '/' ? `${SITE_URL}/` : `${SITE_URL}${path}`;
   const title = meta.title || 'SingleChat';
   const description = meta.description || '';
   const keywords = meta.keywords || '';