[style](trx-frontend-http): remove duplicate logo from login screen

Remove the redundant logo image from the auth gate. The header already
displays the logo, so this duplicate was unnecessary.

The login screen now shows only:
- "Access Required" heading
- "Enter passphrase to continue" subtitle
- Passphrase input
- Login 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/index.html

@@ -28,7 +28,6 @@
     <!-- Auth gate (hidden by default, shown if auth is required) -->
     <div id="auth-gate" style="display:none; padding: 3rem 2rem; text-align: center;">
       <div style="margin-bottom: 1.5rem;">
-        <img src="/logo.png?v=1" alt="trx logo" style="max-width: 80px; margin-bottom: 1rem;" onerror="this.style.display='none'" />
         <div style="font-size: 1.1rem; font-weight: 600; margin-bottom: 0.5rem;">Access Required</div>
         <div style="color: var(--text-muted);">Enter passphrase to continue</div>
       </div>