feat: TenChat auto-posting via refresh token (TCRF) auth

- Rewrite tenchat_publisher to TCRF-only flow: refresh -> Bearer access_token -> publish
- Store only TCRF (one-time refresh token, rotates on each publish)
- Add /tenchat page (GET/POST/disconnect) with username + TCRF fields
- Add publish-to-TenChat button on post publish page
- Update DB helpers: save/get/update/clear tenchat credentials

cabinet_service/templates/profile_edit.html

@@ -22,5 +22,11 @@
     <a href="/provider" class="copy-btn">⚙ Настроить провайдера</a>
 </div>
 
+<div class="card">
+    <h2>TenChat</h2>
+    <p>Подключите аккаунт TenChat, чтобы публиковать посты автоматически.</p>
+    <a href="/tenchat" class="copy-btn">🔑 Настроить TenChat</a>
+</div>
+
 <p><a href="/dashboard">← Назад в кабинет</a></p>
 {% endblock %}