Draft: Handle HelmRelease source type transition

When switching a SylvaUnitsRelease between git and OCI source types, the operator fails with "either chart or chartRef must be set" . When upgrading from Sylva ≤1.5, spec.chart on the HelmRelease is owned by kustomize-controller. The operator's SSA patch adds spec.chartRef without removing spec.chart, violating Flux's mutual-exclusivity constraint.

On reconciliation, detect if the existing HelmRelease spec conflicts with the desired source type (e.g. spec.chart present but OCI is needed). If so, suspend the HelmRelease, remove Flux's finalizer (finalizers.fluxcd.io) to prevent Helm uninstall, delete the HelmRelease, then requeue to recreate it with the correct spec.

closes #78 (closed)