Secret mismatch caused infinite login loop on sizer.dev.t09.de.
Added sizer-oidc-client secret manifest to GitOps so ArgoCD manages it.
Value now matches dex-runner-sizer-client (dex side).
Use short service DNS (garm.garm.svc:80) instead of FQDN
(garm.garm.svc.cluster.local:80) to match what the stack template
now generates.
Ref: IPCEICIS-6886