Bulk User Action

Apply one action to an explicit set of accounts, reporting every skip.

Sync session on purpose: delete reuses purge_user (ordered child-first deletes + the Mollie-cancel backstop), which is sync — reimplementing it in async would be a second, drifting copy of fragile FK-ordering logic. The other three actions are trivial column writes.

Guardrails, all surfaced rather than silent:

• the acting admin and any other admin are never touched (is_admin);
• revoke_grant only ends a grant (REVOCABLE_SOURCES);
• ban/delete refuse on a live paid subscription (_is_paying).

ban sets is_active=False (fastapi-users blocks login on it and the deck drops the account from every count); delete is irreversible.