feat: hide user nav links for admin, redirect admin to /admin/users on login

Connections/Catalog/VK/Sync nav links only shown for regular users or when
admin is viewing as a user. Admin/system users land on /admin/users after login.

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

web/templates/base.html

@@ -16,10 +16,12 @@
             </ul>
             <ul class="nav-links">
                 {% if user %}
+                    {% if user.role not in ('admin', 'system') or viewed_user %}
                     <li><a href="/connections">Подключения</a></li>
                     <li><a href="/catalog">Каталог Эвотор</a></li>
                     <li><a href="/vk-catalog/albums">Каталог ВК</a></li>
                     <li><a href="/sync">Синхронизация</a></li>
+                    {% endif %}
                     {% 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>
@@ -34,10 +36,12 @@
             <details class="mobile-menu">
                 <summary role="button" class="outline secondary icon-btn"><i class="bi bi-list"></i></summary>
                 <ul>
+                    {% if user.role not in ('admin', 'system') or viewed_user %}
                     <li><a href="/connections">Подключения</a></li>
                     <li><a href="/catalog">Каталог Эвотор</a></li>
                     <li><a href="/vk-catalog/albums">Каталог ВК</a></li>
                     <li><a href="/sync">Синхронизация</a></li>
+                    {% endif %}
                     {% if user.role in ('admin', 'system') %}
                     <li><a href="/admin/users">Админ</a></li>
                     <li><a href="/admin/logs">Логи</a></li>