feat: API request/response logging with admin log viewer

- Add api_logs table (migration 0007) and ApiLog model
- Add web/lib/api_logger.py — httpx wrapper that records every outbound call
- Wire api_logger into vk_sync, vk_catalog, and connections test endpoints
- Add /admin/logs page with filters (service, method, status, time range, URL search) and expandable request/response detail
- Add "Логи" nav link for admin users

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

web/templates/base.html

@@ -22,6 +22,7 @@
                     <li><a href="/sync">Синхронизация</a></li>
                     {% if user.role in ('admin', 'system') %}
                     <li><a href="/admin/users"><i class="bi bi-shield-lock"></i> Админ</a></li>
+                    <li><a href="/admin/logs"><i class="bi bi-journal-text"></i> Логи</a></li>
                     {% endif %}
                     <li><a href="/profile"><i class="bi bi-person-circle"></i> Личный кабинет</a></li>
                     <li><a href="/logout" class="secondary">Выход</a></li>
@@ -40,6 +41,7 @@
                     <li><a href="/sync">Синхронизация</a></li>
                     {% if user.role in ('admin', 'system') %}
                     <li><a href="/admin/users">Админ</a></li>
+                    <li><a href="/admin/logs">Логи</a></li>
                     {% endif %}
                     <li><a href="/profile">Личный кабинет</a></li>
                     <li><a href="/logout">Выход</a></li>