feat: add CatalogSale model with abstract base classes for Sale/SaleLine

- Introduced SaleAbstractModel and SaleLineAbstractModel as abstract bases
- Added CatalogSale and CatalogSaleLine models inheriting from them
- Created migration 0045 for new models
- Added CatalogSaleView, CatalogSaleSerializer with nested line creation
- Registered new models in admin
- Added catalog_sales router endpoint to URLs
- Removed placeholder api/ package (now redundant)

tienda_ilusion/don_confiao/api/sale_views.py

@@ -1,5 +0,0 @@
-from rest_framework import viewsets
-
-
-class CatalogSaleView(viewsets.ViewSet):
-    pass