* docs: add Keycloak authentication help articles
- Add AUTH_METHODS_KEYCLOAK.md for en, ru, zh, fa
- Document client setup, role creation, and role mapper configuration
- Include seamless authentication description and troubleshooting
* docs: update Keycloak documentation to match refactored integration
- Replace role-based access with claim-based (remnawaveAccess: true)
- Add Allowed Emails as alternative access control method
- Update field names: keycloakDomain, frontendDomain
- Remove seamlessAuth documentation
- Update troubleshooting section