refactor: remove admin portal link and promote API health check to primary action

Remove admin portal link from public-web landing page actions. Change API health check button from secondary to primary style.

public-web/index.html

@@ -17,8 +17,7 @@
           Use the desktop client to sign in, provision this device, and connect to your private network.
         </p>
         <div class="actions">
-          <a class="button primary" href="https://admin-vpn.nesterovic.cc">Admin portal</a>
-          <a class="button secondary" href="/api/v1/healthz">API health</a>
+          <a class="button primary" href="/api/v1/healthz">API health</a>
         </div>
       </section>