net/keycloak: Update 26.7.4 => 26.8.0

Release Notes:
https://www.keycloak.org/2026/10/keycloak-2680-released

Upgrading Notes:
https://www.keycloak.org/docs/latest/upgrading/index.html#migrating-to-26-8-0

PR: 299044
Approved by: osa, vvd (Mentors, implicit)
Security: CVE-2026-12388
Security: CVE-2026-14781
Security: CVE-2026-19608
Security: CVE-2026-54515
Security: CVE-2026-59889
Security: CVE-2026-59903
MFH: 2026Q4