- New AddUserFormClient on /settings/users (admin-only): username +
password + role select. Wraps createUserAction.
- UserRowClient gains an isLastAdmin prop and a confirm-dialog before
delete. Demote and Delete are both disabled on the last remaining
admin so an admin can't lock everyone out via the UI (server-side
guards in users.ts already cover the API).
- Page passes isLastAdmin per row and computes adminCount once.
- Role badge uses emerald for admin / slate for user; explicit Promote
/ Demote arrows replace the bidirectional icon.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>