remove VPN product CTA blocks, add powered-by footer

Remove {{< vpn-cta >}} shortcode from all 3 language articles
(EN/DE/FR) — editorial VPN mentions kept intact. Footer now shows
"Powered by Agiliton VPN" linking to App Store, plus updated
copyright line.

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

layouts/_default/baseof.html

@@ -45,7 +45,10 @@
       </div>
       <div style="border-top:1px solid #e5e7eb;padding-top:2rem;text-align:center;font-size:0.85rem;color:#6b7280;font-family:system-ui,sans-serif">
         <p>
-          &copy; {{ now.Year }} {{ .Site.Title }}. A publication by <a href="https://www.agiliton.eu" style="color:var(--ifk-accent);text-decoration:none">Agiliton</a>.
+          Powered by <a href="https://go.agiliton.eu/vpn-appstore" style="color:var(--ifk-accent);text-decoration:none">Agiliton VPN</a>
+        </p>
+        <p>
+          &copy; {{ now.Year }} Internet for Kids. A publication by <a href="https://www.agiliton.eu" style="color:var(--ifk-accent);text-decoration:none">Agiliton</a>.
         </p>
         {{ partial "extend-footer.html" . }}
       </div>