Feat: Add catalog page with category tree and product grid

- Create catalog view with recursive category tree building
- Add left-side category tree with expand/collapse functionality
- Add right-side product/kit grid with filtering and search
- Include category navigation with product/kit counts

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

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

myproject/products/urls.py

@@ -8,7 +8,10 @@ app_name = 'products'
 urlpatterns = [
     # Main unified list for products and kits (default view)
     path('', views.CombinedProductListView.as_view(), name='products-list'),
-    
+
+    # Каталог с drag-n-drop
+    path('catalog/', views.CatalogView.as_view(), name='catalog'),
+
     # Legacy URLs for backward compatibility
     path('all/', views.CombinedProductListView.as_view(), name='all-products'),
     path('products/', views.ProductListView.as_view(), name='product-list-legacy'),