feat(analytics): Plausible-Event für Footer-Link-Klick

Trackt „Footer Link Clicked“ beim Klick auf den Autoren-Link im App-Footer.

Co-authored-by: Cursor <cursoragent@cursor.com>

client/src/components/AppFooter.tsx

@@ -1,3 +1,5 @@
+import { PlausibleEvents, trackPlausibleEvent } from '../services/analytics.js'
+
 const APP_VERSION = typeof __APP_VERSION__ !== 'undefined' ? __APP_VERSION__ : 'dev'
 
 export default function AppFooter() {
@@ -9,7 +11,12 @@ export default function AppFooter() {
       </span>
       <span className="app-version-footer__copyright">
         © 2026 KnorrLabs/
-        <a href="mailto:elpatron+kd@mailbox.org">Markus F.J. Busche</a>
+        <a
+          href="mailto:elpatron+kd@mailbox.org"
+          onClick={() => trackPlausibleEvent(PlausibleEvents.FOOTER_LINK_CLICKED)}
+        >
+          Markus F.J. Busche
+        </a>
       </span>
     </footer>
   )