Remove clusterType and adopt valuesFrom overlays for cluster identification

The clusterType field is deprecated in newer CRDs and no longer used by the operator. We will move to context-driven selection via spec.valuesFrom overlays.

What will be done:

Remove spec.clusterType from all SylvaUnitsRelease(Template) manifests.

Add spec.valuesFrom entries (type SylvaUnitsFile) according to the cluster context:

Management → management.values.yaml

Workload → workload-cluster.values.yaml

Bootstrap → management.values.yaml, bootstrap.values.yaml

Bootstrap preview → bootstrap.values.yaml, preview.values.yaml

Workload Preview → bootstrap.values.yaml, workload-cluster.values.yaml

Dependency: Will be coordinated with sylva-units-operator MR [“Use contexts/valuesFrom instead of clusterType” (sylva-projects/sylva-elements/sylva-units-operator!415 (merged))

Acceptance: Templates render without clusterType, include correct overlays, and install successfully with the updated operator.