Add status date to the application status changes API

status_date is now exposed on the Application Status Change resource in API GET responses and on 201 responses for POST /api/v1/application_status_changes. It is the user-set effective date of the change (as shown in the Binti UI). For example, the system might record a transition on 2026-04-10 while the user indicates the status really changed on 2026-03-20 — in that case status_date is 2026-03-20. The field is optional and may be null.

Listing with filters (GET /api/v1/application_status_changes)

• earliest_status_date — only include changes whose effective status_date is on or after this date (inclusive). ISO 8601 date (YYYY-MM-DD).
• latest_status_date — only include changes whose effective status_date is on or before this date (inclusive). ISO 8601 date (YYYY-MM-DD).

You may pass one or both. Bounds are inclusive. Rows with a null status_date are not matched by these filters. If earliest_status_date is after latest_status_date, the result set is empty (not an error)