Closes the gap where "Require login" was effectively admin-only: a member with no
password can't sign in and can't bootstrap one themselves (can't log in to reach
the setting). The set-password endpoint already allowed admin→anyone — this adds
the missing UI.
Each non-admin row in Manage Profiles gets a lock-icon button that opens an inline
form to set / change / remove that member's LOGIN password (separate from the
quick-switch PIN), with a confirm field + a hint explaining when it's used. Admin
rows don't get it (admin manages their own in Settings → Security, which keeps its
anti-lockout). textContent-only rendering, so a profile name can't inject markup.
Test: admin sets a member's password → the member can then authenticate
(verify_profile_password) and a wrong password fails; admin can clear it back to
no-login. 64 script-split integrity tests green.
