fix(products): remove obsolete delete methods from ProductKit

Remove custom delete() and hard_delete() methods that referenced
non-existent is_deleted/deleted_at fields. ProductKit now uses
the correct implementation from BaseProductEntity which uses
status='discontinued' for soft delete.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

myproject/products/models/kits.py

@@ -340,17 +340,6 @@ class ProductKit(BaseProductEntity):
         self.save(update_fields=['is_temporary', 'order'])
         return True
 
-    def delete(self, *args, **kwargs):
-        """Soft delete вместо hard delete - марк как удаленный"""
-        self.is_deleted = True
-        self.deleted_at = timezone.now()
-        self.save(update_fields=['is_deleted', 'deleted_at'])
-        return 1, {self.__class__._meta.label: 1}
-
-    def hard_delete(self):
-        """Полное удаление из БД (необратимо!)"""
-        super().delete()
-
     def create_snapshot(self):
         """
         Создает снимок текущего состояния комплекта.