feat: release v1.8.0 — connections dashboard, VK OAuth, sync config, catalog browser

- Connections dashboard with add/remove flow and background health checks
- VK OAuth connection with profile info and health monitoring
- Sync configuration page with master toggle and filter summary
- Catalog browser with store/group/product tables, filter management, CSV export
- Alembic migrations for all new tables
- run/read_config.py for shell sync script DB integration
- CHANGELOG.md updated for v1.8.0

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

web/templates/base.html

@@ -21,6 +21,12 @@
                         <li class="nav-item">
                             <a href="/connections" class="nav-link">Подключения</a>
                         </li>
+                        <li class="nav-item">
+                            <a href="/catalog" class="nav-link">Каталог</a>
+                        </li>
+                        <li class="nav-item">
+                            <a href="/sync" class="nav-link">Синхронизация</a>
+                        </li>
                         <li class="nav-item">
                             <a href="/profile" class="nav-link"><i class="bi bi-person-circle me-1"></i>Личный кабинет</a>
                         </li>