Laterite auth: backend user authentication and authorization.
Provides the operator-facing security primitives the admin surface is built on: Argon2id password hashing, opaque server-side sessions, a role-based permission model over dotted permission strings, brute-force throttling, and an append-only access log. "Backend users" are the operators of the admin, kept distinct from any application's end users.
This crate is HTTP-agnostic on purpose. It exposes an [AuthService] with
plain async methods (authenticate, verify_session, logout) plus an
[AuthenticatedUser] identity; the admin crate wraps these in Axum
extractors, cookie handling, and the rendered login screen.