feat(chart): add PodDisruptionBudget for HA deployments

[birdmanmandbir]

Summary

Add PodDisruptionBudget to ensure operator availability during voluntary disruptions (node drains, upgrades).

Details

PDB only useful when replicaCount > 1. Should be conditionally rendered.

{{- if gt (int .Values.replicaCount) 1 }}
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: {{ include "cloudnative-supabase.fullname" . }}
spec:
  minAvailable: 1
  selector:
    matchLabels:
      {{- include "cloudnative-supabase.selectorLabels" . | nindent 6 }}
{{- end }}

When This Matters

• Node drains during maintenance
• Cluster upgrades
• Autoscaler scale-downs

Without PDB, all replicas could be evicted simultaneously during multi-node drains.