feat: remove OpenSearch, add ClickHouse admin page

Remove all OpenSearch code, dependencies, configuration, deployment
manifests, and CI/CD references. Replace the OpenSearch admin page
with a ClickHouse admin page showing cluster status, table sizes,
performance metrics, and indexer pipeline stats.

- Delete 11 OpenSearch Java files (config, search impl, admin controller, DTOs, tests)
- Delete 3 OpenSearch frontend files (admin page, CSS, query hooks)
- Delete deploy/opensearch.yaml K8s manifest
- Remove opensearch Maven dependencies from pom.xml
- Remove opensearch config from application.yml, Dockerfile, docker-compose
- Remove opensearch from CI workflow (secrets, deploy, cleanup steps)
- Simplify ThresholdConfig (remove OpenSearch thresholds, database-only)
- Change default search backend from opensearch to clickhouse
- Add ClickHouseAdminController with /status, /tables, /performance, /pipeline
- Add ClickHouseAdminPage with StatCards, pipeline ProgressBar, tables DataTable
- Update CLAUDE.md, HOWTO.md, and source comments

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

deploy/base/server.yaml

@@ -46,10 +46,6 @@ spec:
                 secretKeyRef:
                   name: postgres-credentials
                   key: POSTGRES_PASSWORD
-            - name: OPENSEARCH_URL
-              value: "http://opensearch.cameleer.svc.cluster.local:9200"
-            - name: CAMELEER_OPENSEARCH_INDEX_PREFIX
-              value: "executions-"
             - name: CAMELEER_AUTH_TOKEN
               valueFrom:
                 secretKeyRef:

deploy/opensearch.yaml

@@ -1,98 +0,0 @@
-apiVersion: apps/v1
-kind: StatefulSet
-metadata:
-  name: opensearch
-  namespace: cameleer
-spec:
-  serviceName: opensearch
-  replicas: 1
-  selector:
-    matchLabels:
-      app: opensearch
-  template:
-    metadata:
-      labels:
-        app: opensearch
-    spec:
-      containers:
-        - name: opensearch
-          image: opensearchproject/opensearch:2.19.0
-          ports:
-            - containerPort: 9200
-              name: http
-            - containerPort: 9300
-              name: transport
-          env:
-            - name: discovery.type
-              value: single-node
-            - name: DISABLE_SECURITY_PLUGIN
-              value: "true"
-          volumeMounts:
-            - name: data
-              mountPath: /usr/share/opensearch/data
-          resources:
-            requests:
-              memory: "1Gi"
-              cpu: "200m"
-            limits:
-              memory: "4Gi"
-              cpu: "1000m"
-          livenessProbe:
-            exec:
-              command:
-                - sh
-                - -c
-                - curl -s http://localhost:9200/_cluster/health
-            initialDelaySeconds: 30
-            periodSeconds: 10
-            timeoutSeconds: 5
-            failureThreshold: 3
-          readinessProbe:
-            exec:
-              command:
-                - sh
-                - -c
-                - curl -s http://localhost:9200/_cluster/health
-            initialDelaySeconds: 15
-            periodSeconds: 10
-            timeoutSeconds: 5
-            failureThreshold: 3
-  volumeClaimTemplates:
-    - metadata:
-        name: data
-      spec:
-        accessModes: ["ReadWriteOnce"]
-        resources:
-          requests:
-            storage: 10Gi
----
-apiVersion: v1
-kind: Service
-metadata:
-  name: opensearch
-  namespace: cameleer
-spec:
-  clusterIP: None
-  selector:
-    app: opensearch
-  ports:
-    - port: 9200
-      targetPort: 9200
-      name: http
-    - port: 9300
-      targetPort: 9300
-      name: transport
----
-apiVersion: v1
-kind: Service
-metadata:
-  name: opensearch-external
-  namespace: cameleer
-spec:
-  type: NodePort
-  selector:
-    app: opensearch
-  ports:
-    - port: 9200
-      targetPort: 9200
-      nodePort: 30920

deploy/overlays/feature/kustomization.yaml

@@ -25,8 +25,6 @@ patches:
                 env:
                   - name: CAMELEER_DB_SCHEMA
                     value: "BRANCH_SCHEMA"
-                  - name: CAMELEER_OPENSEARCH_INDEX_PREFIX
-                    value: "cam-BRANCH_SLUG-executions-"
                   - name: CAMELEER_UI_ORIGIN
                     value: "http://BRANCH_SLUG.cameleer.siegeln.net"
   # UI ConfigMap: branch-specific API URL

deploy/overlays/main/kustomization.yaml

@@ -40,8 +40,6 @@ patches:
                 env:
                   - name: SPRING_DATASOURCE_URL
                     value: "jdbc:postgresql://postgres:5432/cameleer3?currentSchema=public"
-                  - name: OPENSEARCH_URL
-                    value: "http://opensearch:9200"
                   - name: CAMELEER_UI_ORIGIN
                     value: "http://192.168.50.86:30090"
   # UI ConfigMap: production API URL