Introduce the foundational accounts app:
- Custom email-as-username User (AbstractBaseUser + PermissionsMixin) set
as AUTH_USER_MODEL, decoupled from membership so children can be members
without a login.
- Member model holding personal/roster data (names, contact email, phone +
emergency phone via django-phonenumber-field, license number, DOB) with an
optional link to a User.
- Family household grouping and directional Guardianship (guardian -> child)
with uniqueness and no-self-guardian constraints.
- Custom UserAdmin plus Member/Family admin with inlines and autocomplete.
- Settings: register apps, AUTH_USER_MODEL, phonenumber defaults (BE/E164).
- Add CLAUDE.md and a tracked static/ directory.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
