Client - Assign a new party code to prior and subsequent registrations

As a client user of the PPR, I want to assign a new party code to both prior and subsequent registrations, so that I can manage transfers or restructuring across multiple records efficiently.

No files, tests, or entry points are identified in the issue. First clarify the PPR registration and party-code workflows, then locate the client-side entry point and related tests; done means a client user can assign a new party code to both prior and subsequent registrations across the relevant transfer or restructuring records.

Written by the indexing model from the issue text.