Adds expand-replicas-job.yaml: PostSync hook Job that:
- Waits for all 3 Longhorn nodes to be Ready
- Patches every volume with numberOfReplicas < 3 to 3
- Runs idempotently on every longhorn-config sync (BeforeHookCreation
deletes previous job, so re-runs are safe)
This ensures existing 1-replica volumes (created before the HA setup) get
expanded automatically via GitOps, not via manual kubectl patch.
Why PostSync: needs to run AFTER the taint-toleration setting and Node CRDs
are applied, otherwise there aren't 3 nodes available yet and the expansion
would fail (Longhorn can't create replicas on nodes that don't exist).