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/db-service.yaml

@@ -0,0 +1,21 @@
+{{- if .Values.database.enabled }}
+{{- $ns     := include "cloudhost-app.namespace" . -}}
+{{- $dbName := include "cloudhost-app.dbDeploymentName" . -}}
+{{- $dbPort := include "cloudhost-app.dbPort" . -}}
+apiVersion: v1
+kind: Service
+metadata:
+  name: {{ $dbName }}
+  namespace: {{ $ns }}
+  labels:
+    app: {{ $dbName }}
+    {{- include "cloudhost-app.labels" . | nindent 4 }}
+spec:
+  type: ClusterIP
+  selector:
+    app: {{ $dbName }}
+  ports:
+    - port: {{ include "cloudhost-app.dbPort" . | int }}
+      targetPort: {{ include "cloudhost-app.dbPort" . | int }}
+      protocol: TCP
+{{- end }}