Contract Signature Reminder Organization Name = None

Covers the class of bugs where a counterparty CONTRACT_SIGNATURE_REMINDER email renders the reminder copy as:

This is a reminder to sign ... sent to you by None ...

or shows the wrong organization in that same line.

Root Cause

This is a reminder-body context issue, not necessarily an email sender identity issue.

SendSignatureReminderEmailUseCase._get_additional_context() populates organization_name, which is used in the body template:

This is a reminder to sign ... sent to you by {{organization_name|bold_text}} ...

Before the fix, counterparty reminders could use request_data.contract_role.organization_entity_name, which is the recipient role's organization entity name. In affected contracts, that value could be missing or unsuitable, so the rendered email showed None or an incorrect organization.