Staff - Create new secured party code

#### User Story
As a registry staff member,
I want to create a secured party code on behalf of a client,
So that I can ensure the code is properly structured, avoids duplication, and supports the client's registration needs.

#### Acceptance Criteria
Given a client requests a new secured party code via Form 3,
When I search the existing codes by name, address, or related identifiers,
Then I should be able to confirm whether a code already exists or if a new one is needed.

Given no existing code is found or a new code is justified,
When I proceed to create the code,
Then I should be able to specify whether it is a parent or child code and link it accordingly.

Given I am entering the client’s information,
When I submit the form,
Then the system should validate the data (e.g., legal name, address format) and assign the next sequential code number.

Given the code is successfully created,
When I complete the process,
Then the client should receive confirmation with their new secured party code and any relevant instructions (**automated? or just a manual process?**)

The issue names no files, tests, or entry points. Start by reviewing the existing staff workflow for Form 3 and secured party codes, then clarify how searches, parent/child linking, validation, sequential numbering, and confirmation should work. Done means the full creation flow meets the acceptance criteria and the automated-versus-manual confirmation step is decided.

Written by the indexing model from the issue text.