…instance migration

Kube-OVN reads MAC address exclusively from the pod annotation
ovn.kubernetes.io/mac_address, not from the IP resource spec.macAddress.
Without pod-level annotations, migrated VMs receive a new random MAC,
breaking OS-level network config that matches by MAC (e.g. netplan).

Add a Helm lookup for the Kube-OVN IP resource in the vm-instance chart
template. When the IP resource exists, its macAddress and ipAddress are
automatically injected as pod annotations. This removes the need for
fragile Flux postRenderers on the HelmRelease — the chart itself handles
MAC/IP preservation based on actual cluster state.

Remove the postRenderers approach from migration 29 since the chart now
handles this natively.

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: Kirill Ilin <stitch14@yandex.ru>
(cherry picked from commit 9a4f492)