Configuration version pinning strategy on Velero restore

[patrick-hermann-sva]

Parent: #111

Problem: a control plane restored from Velero gets its MRs back at version N, but Flux pulls the latest Configuration OCI tag → potential spec drift between restored MRs and new Composition.

Options

1. Pin per cluster via EnvironmentConfig or per-shard Flux Kustomization values (deterministic, more config to manage)
2. Accept latest-Configuration semantics on restore (simpler, must be documented; risk of immediate reconciliation churn post-restore)
3. Hybrid: pin majors, float minors

Deliverable

ADR + runbook section.