fix: show user nav (not admin nav) when impersonating a user

When viewed_user is set, the sidebar should render the full user
navigation (connections, catalog, sync, profile) instead of the
admin-only panel.

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

web/templates/base.html

@@ -35,13 +35,13 @@
 
     <nav class="sb-nav">
       {% if user %}
-        {% if user.role in ('admin', 'system') %}
+        {% if user.role in ('admin', 'system') and not viewed_user %}
         <div class="sb-section">Управление</div>
         <a href="/admin/users" class="sb-item {% if request.url.path.startswith('/admin/users') %}active{% endif %}">
           <span class="sb-icon"><i class="bi bi-people"></i></span>
           <span>Пользователи</span>
         </a>
-        {% if user.role == 'system' %}
+        {% if user.role in ('admin', 'system') %}
         <a href="/admin/logs" class="sb-item {% if request.url.path.startswith('/admin/logs') %}active{% endif %}">
           <span class="sb-icon"><i class="bi bi-journal-text"></i></span>
           <span>Логи</span>