phsl / new-api

/api/status never returned `register_enabled` or `password_register_enabled`,
so the sign-in page had no way to react when an admin disabled registration.
The "Sign up" link was only gated on `self_use_mode_enabled`, which is a
separate and unrelated concept (single-user vs. multi-user deployment).

Result: toggling "Registration Enabled" in admin settings had no visible
effect on the login page — users could still see the sign-up link even when
registration was disabled, and could not see it even when it was enabled
(if the system happened to be in self-use mode from initial setup).

Fix:
- Add `register_enabled` and `password_register_enabled` to GetStatus()
- Gate the "Sign up" link on `register_enabled !== false` in addition to
  the existing `!self_use_mode_enabled` check

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>