feat(20-03): add MemberEditorSheet with edit/create modes and per-section saves
- Edit mode: Profile (display name + admin toggle), Set new password, App password sections
- Create mode: single form with display name, username, initial/confirm password
- Per-section saves keep sheet open; create success closes sheet (D-05, D-07)
- Admin toggle role=switch, aria-checked; last-admin 409 shows inline error + reverts (D-03)
- Section 2 gated on member.hasLocalCredential; passwords never prefilled (T-20-07)
- App password save routes through saveCredential -> CalDAV validation (T-20-08)
- No Rotate/Add credential/Reset password copy (D-06)
Lucas Berger
b125a69b58