feat: add user roles management UI with owner access control

- Added role management views (list, create, edit, delete)
- Created user_roles URL routing
- Added role management templates with Bootstrap styling
- Updated navbar with Roles link for owners and superusers
- Enhanced decorators and mixins with superuser bypass
- Added assign_owner_role.py utility script

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

myproject/myproject/urls.py

@@ -17,6 +17,7 @@ urlpatterns = [
     # Web interface for shop owners
     path('', views.index, name='index'),  # Главная страница
     path('accounts/', include('accounts.urls')),  # Управление аккаунтом
+    path('roles/', include('user_roles.urls')),  # Управление ролями пользователей
     path('products/', include('products.urls')),  # Управление товарами
     path('customers/', include('customers.urls')),  # Управление клиентами
     path('inventory/', include('inventory.urls')),  # Управление складом