net/keycloak: Update 26.6.2 => 26.6.3 (16 CVEs)

Release Notes:
https://www.keycloak.org/2026/06/keycloak-2663-released

PR: 295858
Security: CVE-2026-4800
Security: CVE-2026-4874
Security: CVE-2026-37977
Security: CVE-2026-7500
Security: CVE-2026-42581
Security: CVE-2026-8922
Security: CVE-2026-8830
Security: CVE-2026-9088
Security: CVE-2026-9087
Security: CVE-2026-9802
Security: CVE-2026-9794
Security: CVE-2026-9791
Security: CVE-2026-0707
Security: CVE-2026-9801
Security: CVE-2026-9704
Security: CVE-2026-9792
Sponsored by: UNIS Labs
MFH: 2026Q2

(cherry picked from commit 8861c99f200810422ebe8c6403af297b774f5d56)