helm: improvements (#10976)

- fix(ingress): use root context ($) for fullname inside range
- fix(statefulset): use updateStrategy instead of strategy for
mysql/infinity/elasticsearch/opensearch
- feat(mysql): add external mode via mysql.enabled=false with env
MYSQL_HOST/PORT and MYSQL_USER (default root)
- feat(minio/redis): add external mode via *.enabled=false with env
*_HOST/PORT
- feat(global): add global.repo for image registry prefix and
global.imagePullSecrets for all pods
- feat: helper template ragflow.imageRepo to render image with global
repo
- chore(env): allow optional MINIO_HOST, MINIO_PASSWORD, REDIS_PASSWORD
(remove required); keep MYSQL_PASSWORD required
- docs(helm): add helm/README.md and update usage
- refactor(images): apply global repo to all components and init
containers
- test: align test busybox image with global repo helper

### What problem does this PR solve?

_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)
- [x] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

helm/templates/redis.yaml

@@ -1,3 +1,4 @@
+{{- if .Values.redis.enabled }}
 ---
 apiVersion: v1
 kind: Service
@@ -40,9 +41,9 @@ spec:
       annotations:
         checksum/config-env: {{ include (print $.Template.BasePath "/env.yaml") . | sha256sum }}
     spec:
-      {{- if or .Values.imagePullSecrets .Values.redis.image.pullSecrets }}
+      {{- if or .Values.global.imagePullSecrets .Values.redis.image.pullSecrets }}
       imagePullSecrets:
-        {{- with .Values.imagePullSecrets }}
+        {{- with .Values.global.imagePullSecrets }}
         {{- toYaml . | nindent 8 }}
         {{- end }}
         {{- with .Values.redis.image.pullSecrets }}
@@ -52,7 +53,7 @@ spec:
       terminationGracePeriodSeconds: 60
       containers:
         - name: redis
-          image: {{ .Values.redis.image.repository }}:{{ .Values.redis.image.tag }}
+          image: {{ include "ragflow.imageRepo" (dict "root" . "repo" .Values.redis.image.repository) }}:{{ .Values.redis.image.tag }}
           {{- with .Values.redis.image.pullPolicy }}
           imagePullPolicy: {{ . }}
           {{- end }}
@@ -131,3 +132,4 @@ spec:
     matchLabels:
       {{- include "ragflow.selectorLabels" . | nindent 6 }}
       app.kubernetes.io/component: redis
+{{- end }}