feat(helm): add cloudhost-app Helm chart for all runtimes

- deployment.yaml with imagePullSecrets, health probes, WordPress volumes
- db-deployment.yaml for PostgreSQL/MySQL with readiness/liveness probes
- ingress.yaml with cert-manager TLS
- registry-pull-secret.yaml for insecure registries
- PVCs and secrets with helm.sh/resource-policy: keep
- _helpers.tpl with shared template functions
- values.yaml with comprehensive defaults

backend/helm/cloudhost-app/templates/wp-pvc.yaml

@@ -0,0 +1,19 @@
+{{- if .Values.wordpress.enabled }}
+{{- $name := include "cloudhost-app.name" . -}}
+{{- $ns   := include "cloudhost-app.namespace" . -}}
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: {{ $name }}-wp-content
+  namespace: {{ $ns }}
+  labels:
+    {{- include "cloudhost-app.labels" . | nindent 4 }}
+  annotations:
+    "helm.sh/resource-policy": keep
+spec:
+  accessModes:
+    - ReadWriteOnce
+  resources:
+    requests:
+      storage: {{ .Values.wordpress.wpContentStorageSize | quote }}
+{{- end }}