Fix: newsletter inside login panel (right sidebar), show it for non-logged-in users; hide both after login

index.html

@@ -247,8 +247,8 @@
         </div>
       </aside>
 
-      <aside class="sidebar-col hidden" id="newsletter-panel">
-        <div class="newsletter-panel">
+      <aside class="sidebar-col" id="newsletter-panel">
+        <div class="newsletter-panel hidden">
           <h3 class="hide-de">Newsletter</h3>
           <h3 class="hide-en">Newsletter</h3>
           <form id="newsletter-form">
@@ -323,6 +323,7 @@
       } else {
         if (notebook) notebook.classList.add('hidden');
         if (login) login.classList.remove('hidden');
+        // Newsletter is hidden by default in HTML (newsletter-panel hidden), show it when not logged in
         if (newsletter) newsletter.classList.remove('hidden');
       }
     }