docs/mobile.md had grown past a thousand lines and still described the
SSO-preserving logout replaced by the IdP round-trip, while the
identity / Play publishing tooling, versioning, OTA publishing from
Scalingo, rollback and the HTTPS CSRF Origin constraint were
undocumented. mobile.md now covers the development workflow only;
release, versioning, OTA publishing and rollback move to
docs/mobile-release.md, and the references in code and env.md follow.