fix: update VPN CTA links to go.agiliton.eu/vpn redirect service

Replaces broken agiliton.eu/vpn links with tracked redirect via
go.agiliton.eu, which fires Rybbit analytics before forwarding
to the App Store.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

layouts/partials/vpn-cta.html

@@ -7,7 +7,7 @@
     Agiliton VPN provides content filtering, device protection, and safe browsing for the whole family.
     {{ end }}
   </p>
-  <a href="https://www.agiliton.eu/vpn" style="display: inline-block; background: #fff; color: #1a365d; padding: 0.75rem 2rem; border-radius: 8px; text-decoration: none; font-weight: 600;">
+  <a href="https://go.agiliton.eu/vpn" style="display: inline-block; background: #fff; color: #1a365d; padding: 0.75rem 2rem; border-radius: 8px; text-decoration: none; font-weight: 600;">
     {{ if eq .Language.Lang "de" }}Mehr erfahren{{ else }}Learn More{{ end }}
   </a>
 </aside>