[fix](trx-frontend-http): show guest button after logout when available

After logout, check if guest mode is available and show the
"Continue as Guest" button if no rx_passphrase is configured.

Previously, authLogout() always passed false to showAuthGate(),
hiding the guest button.

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

@@ -54,7 +54,11 @@ async function authLogout() {
     document.getElementById("loading").style.display = "none";
     document.getElementById("auth-passphrase").value = "";
     updateAuthUI();
-    showAuthGate(false);
+
+    // Check if guest mode is available after logout
+    const authStatus = await checkAuthStatus();
+    const allowGuest = authStatus.role === "rx";
+    showAuthGate(allowGuest);
   } catch (e) {
     console.error("Logout failed:", e);
     showAuthError("Logout failed");