[fix](trx-frontend-http): hide all tab panels when showing auth gate

When logout is clicked from the About tab, hide all tab panels to
prevent tab content from showing behind the login window.

Also ensures auth gate is displayed cleanly without any stray content
visible behind it.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Stanislaw Grams <stanislawgrams@gmail.com>

src/trx-client/trx-frontend/trx-frontend-http/assets/web/app.js

@@ -71,6 +71,11 @@ function showAuthGate(allowGuest = false) {
   document.getElementById("auth-gate").style.display = "block";
   document.getElementById("tab-bar").style.display = "none";
 
+  // Hide all tab panels
+  document.querySelectorAll(".tab-panel").forEach(panel => {
+    panel.style.display = "none";
+  });
+
   // Show guest button if guest mode is available
   const guestBtn = document.getElementById("auth-guest-btn");
   if (guestBtn) {