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/workers.yaml

@@ -0,0 +1,47 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: spark-worker
+  labels:
+    app.kubernetes.io/name: spark-worker
+    app.kubernetes.io/part-of: nowchess
+spec:
+  replicas: 2
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: spark-worker
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/name: spark-worker
+        app.kubernetes.io/part-of: nowchess
+    spec:
+      containers:
+        - name: spark-worker
+          image: apache/spark:3.5.4-scala2.13-java17-ubuntu
+          command:
+            - /opt/spark/bin/spark-class
+            - org.apache.spark.deploy.worker.Worker
+            - spark://spark-master:7077
+          env:
+            - name: SPARK_WORKER_CORES
+              value: "1"
+            - name: SPARK_WORKER_MEMORY
+              value: "1g"
+          ports:
+            - name: webui
+              containerPort: 8081
+          resources:
+            requests:
+              cpu: 500m
+              memory: 1Gi
+            limits:
+              cpu: "1"
+              memory: 2Gi
+          volumeMounts:
+            - name: spark-events
+              mountPath: /spark-events
+      volumes:
+        - name: spark-events
+          persistentVolumeClaim:
+            claimName: spark-events