* fix(auth): let deployments close local self-registration
The OIDC provisioning policy (allowed_email_domains, require_verified_email,
auto_create_users) is enforced only in the SSO callback via
get_or_provision_oidc_user. POST /api/v1/auth/register creates a local account
without consulting any of it, and nothing can turn that path off, so a
deployment declaring an email-domain allowlist can still be joined by any
address through local registration.
Add auth.local.allow_registration (default true, so existing deployments are
unchanged) and gate /register on it before the account is created. Report the
flag from /setup-status so the login page stops offering a signup entry the
Gateway will reject.
/initialize is deliberately not gated: it is the bootstrap path, guarded by
admin_count == 0, and closing it would leave a fresh install unable to create
its first admin.
An unreadable config.yaml falls back to the pre-gate default (open) rather than
making these two endpoints a hard dependency on the file.
* docs(auth): align registration-gate fallback wording with the FileNotFoundError catch
