Invariant: while security.require_login is on, every profile must have a login
password or it's locked out. Previously only the admin's own anti-lockout existed,
so members could be stranded (created without a password, or login flipped on while
passwordless members existed). Closed all the write-points:
core/security/login_provisioning.py (pure policy, single source of truth):
- members_without_password(profiles) — non-admin profiles that can't sign in
- create_needs_password(require_login) / removing_password_strands(require_login)
Wired into web_server:
- create_profile: while login is on, a new member must be given a password (400
otherwise) and it's set on creation.
- enable-login (settings save): refuses to turn login on while any member lacks a
password — lists them — same shape as the existing admin anti-lockout.
- set-password: refuses to CLEAR a password while login is on (would strand them).
UI: Create Profile form gains a login-password field (alongside the optional PIN);
the Manage Profiles per-member password button (prior commit) covers existing
members + changes.
Tests: pure policy seam + endpoint enforcement (create blocked w/o password when
on, allowed w/ password, no friction when off, clear blocked when on). 442
profile/settings/auth tests green; ruff clean.
