v3.2.6-sr94.29: Configuration-aware login copy

Configuration-Aware Login Copy

The header and page title no longer advertise sign-up when no registration control is available. SSO-only/local-only deployments say Log in; a closed login has an explicit title and no header sign-in entry. Email-verification return links use the same copy. The local form derives its sign-up control from the same configuration.

No authentication policy, OIDC setting, API denial status, database schema, dependency, secret or public redirect behavior changes. Refresh open login pages after deployment. Image-only rollback preserves current data but restores misleading copy.

Validation covers seven isolated server configurations with unchanged disabled-feature denial and public redirects, plus desktop/390px/320px browser flows for SSO-only, local-only, registration-enabled and closed login. Publication, exact-image and homelab deployment/recovery gates remain separately tracked in docs/UI-UX-REVIEW.md; do not equate publication with deployment acceptance.