local-path provisioner is RWO-only; attaching a single PVC to master, two
workers, history-server, and streaming pod on separate nodes causes
Multi-Attach errors. Each pod now gets its own ephemeral emptyDir for
/spark-events. Event logging confs removed from CronJobs and streaming
Deployment (logs are pod-local and do not persist across restarts).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>