Add none method to FakeQuerySet

[engineervix]

This PR implements the none() method on FakeQuerySet to match Django's QuerySet API.

Motivation

Django's QuerySet has a none() method that returns an empty queryset. This is useful for:

• Conditional query building where you want to explicitly return nothing
• Testing code that uses .none()
• API completeness with Django's QuerySet interface

Currently, FakeQuerySet doesn't implement this method, which can cause issues when testing code that uses it.

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Django implementation: https://github.com/django/django/blob/2b0f24e6/django/db/models/query.py#L1604