feat(spark): replace Bitnami chart with Apache Spark manifests

Bitnami Spark chart requires a Broadcom commercial license. Replace with
plain Deployments using apache/spark:3.5.4-scala2.13-java17-ubuntu
(Apache 2.0, same image used by the analytics jobs):
- spark-master: Deployment + ClusterIP Service (ports 7077/8080)
- spark-worker: Deployment, 2 replicas, connects to spark-master:7077
- spark-history-server: updated to apache/spark image
Ingress backend corrected to spark-master:8080.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

spark-cluster/base/kustomization.yaml

@@ -3,58 +3,7 @@ kind: Kustomization
 
 resources:
   - pvc.yaml
+  - master.yaml
+  - workers.yaml
   - history-server.yaml
   - ingress.yaml
-
-helmCharts:
-  - name: spark
-    repo: https://charts.bitnami.com/bitnami
-    version: "9.2.10"
-    releaseName: spark
-    namespace: nowchess
-    valuesInline:
-      master:
-        resources:
-          requests:
-            cpu: 500m
-            memory: 1Gi
-          limits:
-            cpu: "1"
-            memory: 2Gi
-        extraVolumes:
-          - name: spark-events
-            persistentVolumeClaim:
-              claimName: spark-events
-        extraVolumeMounts:
-          - name: spark-events
-            mountPath: /spark-events
-      worker:
-        replicaCount: 2
-        resources:
-          requests:
-            cpu: 500m
-            memory: 1Gi
-          limits:
-            cpu: "1"
-            memory: 2Gi
-        extraVolumes:
-          - name: spark-events
-            persistentVolumeClaim:
-              claimName: spark-events
-        extraVolumeMounts:
-          - name: spark-events
-            mountPath: /spark-events
-      historyServer:
-        enabled: true
-        eventsDir: /spark-events
-        extraVolumes:
-          - name: spark-events
-            persistentVolumeClaim:
-              claimName: spark-events
-        extraVolumeMounts:
-          - name: spark-events
-            mountPath: /spark-events
-      ingress:
-        enabled: false
-      service:
-        type: ClusterIP