Ministry User Changes Effective Date of PD/PPD

**User Story**
As a Ministry User, I want to be able to select an effective date when entering a student's PD/PPD status in SIMS, and I want to be able to change that effective date at any time. This allows for backdating of effective dates in instances where their disability status was made effective long ago but only inputted recently.

Start by locating the SIMS workflow for entering a student's PD/PPD status and any existing effective-date handling. Confirm how Ministry Users should select, edit, and backdate the date, then identify the affected tests; done means the date can be set and changed at any time with the expected validation and persistence.

Written by the indexing model from the issue text.