Extend the delete_deleted_user_resources() trigger so that secrets
belonging to a soft-deleted user are removed in the same transaction as
the existing api_keys and user_links cleanup.
user_secrets.user_id has ON DELETE CASCADE, but Coder soft-deletes users
by flipping users.deleted rather than removing the row, so the foreign key
cascade never fires and secrets would otherwise survive deletion.
Assisted by Coder Agents.
Zach