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/history-server.yaml

@@ -18,10 +18,9 @@ spec:
     spec:
       containers:
         - name: history-server
-          # Same image version the Bitnami chart deploys for master/workers.
-          image: docker.io/bitnami/spark:3.5.2
+          image: apache/spark:3.5.4-scala2.13-java17-ubuntu
           command:
-            - /opt/bitnami/spark/bin/spark-class
+            - /opt/spark/bin/spark-class
             - org.apache.spark.deploy.history.HistoryServer
           env:
             - name: SPARK_HISTORY_OPTS