Redesign: Start/Stop buttons, locked settings, queue countdown, wb2 logo

- Replace tumbler with Start/Stop buttons (green/red)
- Lock settings form with <fieldset disabled> when auto-reply active
- Clear queue + reset fetch timer on settings save
- Show 'Очередь подгрузится через X сек.' countdown in queue section
- API /status returns next_fetch_seconds, queue_len, auto_reply_enabled
- Login: price 15₽/день, up to 144 replies/day, wb2 logo, promo panel 25% width
- Replace wb.png → wb2.png across all templates

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

templates/cabinet.html

@@ -11,7 +11,7 @@
 <nav class="topbar">
     <div class="topbar__inner">
         <a href="{{ url_for('index') }}" class="topbar__brand">
-            <img src="{{ url_for('static', filename='wb.png') }}" class="topbar__logo-img" alt="WB">
+            <img src="{{ url_for('static', filename='wb2.png') }}" class="topbar__logo-img" alt="WB">
             <span class="topbar__name">Feedback</span>
         </a>
         <div class="topbar__nav">