Enable Change End Date for $0 Plans as before

PROBLEM STATEMENT

Currently admins have no way to change the end date of a subscription with 0$ plan. This limitation prevents accurate record-keeping for accounts that were active in the past, makes it difficult to retroactively correct subscription timelines, and creates inconsistencies in billing history and reporting for free-tier accounts.

USER STORY

As an admin,

I want to set a change end date for the subscription if a plan is 0$,

So that I can accurately reflect the true subscription timeline and maintain clean historical records.

DEFINITION OF DONE

- Admins can change the end date for $0 plans on unabstracted accounts.

- Changing end date (shortening) is available via the admin dashboard on the subscription edit view.

- Billing exports and reports accurately reflect the new end date.

- Tested across relevant browsers and devices.

- Documentation updated accordingly.