Add /admin/users to create, edit, disable and delete accounts with the
per-area permission grid. New users get a one-time invite link (48 h)
by email; the admin also sees it once, so an account without email can
still be onboarded. Forgotten passwords get a 1 h reset link with the
same answer for unknown accounts. Only token hashes are stored.
Guards against escalation and lockout: a user manager can only grant
flags they hold and cannot touch flags they lack; only superusers change
superuser accounts; nobody can disable or delete themselves; the last
active superuser stays.
Logins, user changes, and bingo and invoice actions are recorded in an
audit log at /admin/audit.
Read timestamps as UTC: they are all written with Time.now.utc, and on a
UTC+4 host a fresh 1 h token read back as already expired.
Assisted-by: Claude:opus-5
