fix: resolve critical deployment issues across Helm charts, Dockerfile, and K8s fallback

- Add helm/kubectl binaries and chart directory to backend Dockerfile
- Extend Helm templates for MongoDB/MariaDB database support (env vars, probes, ports)
- Add Redis and RabbitMQ Helm templates (deployment, service, secret, PVC)
- Add generic app-storage PVC and Fluent Bit sidecar with ES authentication
- Fix imagePullSecrets in K8s API fallback, prevent secret regeneration on redeploy
- Clean up Redis/RabbitMQ/FluentBit resources on app deletion without removing shared secrets
- Fix HelmService chartPath resolution for production Docker builds

Co-authored-by: Cursor <cursoragent@cursor.com>

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

@@ -0,0 +1,17 @@
+{{- $name := include "cloudhost-app.name" . -}}
+{{- $ns   := include "cloudhost-app.namespace" . -}}
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: {{ $name }}-storage
+  namespace: {{ $ns }}
+  labels:
+    {{- include "cloudhost-app.labels" . | nindent 4 }}
+  annotations:
+    "helm.sh/resource-policy": keep
+spec:
+  accessModes:
+    - ReadWriteOnce
+  resources:
+    requests:
+      storage: {{ .Values.app.storageSize | default "2Gi" | quote }}