feat(spark): deploy persistent Spark cluster with Web UI

- Add spark-cluster/base with Bitnami Spark chart 9.2.10 (master +
  2 workers), spark-events PVC (RWO/local-path), and Ingress resources
  for spark.nowchess.janis-eccarius.de (master UI) and
  spark-history.nowchess.janis-eccarius.de (history placeholder)
- Add spark-cluster/eu-central-1-prod overlay and ArgoCD Application
  (automated prune + selfHeal)
- Migrate all spark-analytics CronJobs and streaming Deployment from
  K8s-native mode (k8s://...) to Spark standalone (spark://spark-master:7077);
  drop kubernetes-specific --conf flags; add eventLog confs; mount
  spark-events PVC on all job pods

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

spark-cluster/base/charts/spark-9.2.10/spark/Chart.yaml

@@ -0,0 +1,29 @@
+annotations:
+  category: Infrastructure
+  images: |
+    - name: spark
+      image: docker.io/bitnami/spark:3.5.2-debian-12-r1
+  licenses: Apache-2.0
+apiVersion: v2
+appVersion: 3.5.2
+dependencies:
+- name: common
+  repository: oci://registry-1.docker.io/bitnamicharts
+  tags:
+  - bitnami-common
+  version: 2.x.x
+description: Apache Spark is a high-performance engine for large-scale computing tasks,
+  such as data processing, machine learning and real-time data streaming. It includes
+  APIs for Java, Python, Scala and R.
+home: https://bitnami.com
+icon: https://bitnami.com/assets/stacks/spark/img/spark-stack-220x234.png
+keywords:
+- apache
+- spark
+maintainers:
+- name: Broadcom, Inc. All Rights Reserved.
+  url: https://github.com/bitnami/charts
+name: spark
+sources:
+- https://github.com/bitnami/charts/tree/main/bitnami/spark
+version: 9.2.10