feat: add product activation/deactivation and filtering by active status

- Add 'active' boolean field to Product model with default=True
- Implement ProductView.get_queryset() to filter products by active status
  - Default behavior: return only active products
  - Support query params: ?active=true|false|all
  - Support variations: 1/0, yes/no for true/false
  - Detail operations (GET/PATCH/DELETE by ID) work with all products
- Update ProductSerializer to include 'active' field
- Add comprehensive test suite (11 new tests):
  - Test filtering by active/inactive/all products
  - Test parameter variations (1, yes, 0, no)
  - Test PATCH to activate/deactivate products
  - Test default list behavior after status changes
- Update API documentation in doc/requests.org with examples
- All tests passing (13 product tests + 8 API tests)

tienda_ilusion/don_confiao/models/products.py

@@ -14,6 +14,7 @@ class ProductCategory(models.Model):
 
 
 class Product(models.Model):
+    active = models.BooleanField(default=True)
     name = models.CharField(max_length=100, unique=True)
     price = models.DecimalField(max_digits=9, decimal_places=2)
     measuring_unit = models.CharField(