F-187 — Admin can deactivate and delete POS cashiers

Allow administrators to safely remove cashier access without breaking historical POS attribution.

Scope

Add an explicit active/deactivated/deleted lifecycle for backoffice POS cashier accounts.
Show POS cashiers and their status in the TPV administration page.
Let admins create cashiers, deactivate/reactivate them, and delete them with explicit confirmation.
Treat delete as an irreversible soft deletion: preserve the backoffice user row and its ID so sessions, sales, receipts, reporting and audit history keep their cashier attribution.
Revoke every live backoffice session when a cashier is deactivated or deleted.
Reject login and existing-session authentication for inactive or deleted accounts.
Reject deactivation/deletion while the cashier owns an open cash session; require the cash session to be closed first.
Keep all lifecycle mutations admin-only and cashier-role-only.

Admin TPV lists POS cashiers with active, inactive or deleted status.
Admin can create a cashier and the account is active by default.
Admin can deactivate an active cashier and reactivate an inactive non-deleted cashier.
Deactivation immediately revokes existing sessions and blocks future login/authentication.
Admin can delete a cashier only after explicit confirmation; deleted cashiers cannot be reactivated or authenticate.
Deactivation or deletion is rejected while the cashier has an open cash session.
Deletion preserves the cashier row/ID and all historical session, sale, receipt and reporting attribution.
Non-admin users cannot list or mutate cashier lifecycle, and non-cashier roles cannot be targeted.
Migration is reversible and existing backoffice accounts remain active.
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