users: unify ylw as common admin, keep host-specific passwords and groups
...
Move ylw base identity (isNormalUser, wheel, SSH key) to modules/users.nix
alongside ldx. Host configs retain only extra groups and hashedPassword.
Also renames ye-lw21 to ylw on skydick.
Co-Authored-By: Claude Opus 4.6 <[email protected]>