net/traefik: Update to upstream release 3.6.8
Details:
- Bugfix release, see https://github.com/traefik/traefik/releases/tag/v3.6.8
- Includes a fix for CVE-2026-25949, a potential DoS
MFH: 2026Q1
Security: CVE-2026-25949
(cherry picked from commit f164467debd4f96830fe08297306d502f03b1c3f)