fix: co-locate analytics driver pods with spark-worker for RWO PVC access

do-block-storage only supports ReadWriteOnce. Executor tasks failed with
`Mkdirs failed` because the executor ran on the spark-worker node which
had no mount of the spark-analytics-output PVC.

- Mount spark-analytics-output PVC on spark-worker pod at /spark-output
- Add podAffinity to all 11 analytics CronJob driver pods to schedule on
  the same node as spark-worker, ensuring the RWO PVC is accessible by
  both driver and executor

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

spark-cluster/base/workers.yaml

@@ -41,6 +41,11 @@ spec:
           volumeMounts:
             - name: spark-events
               mountPath: /spark-events
+            - name: spark-output
+              mountPath: /spark-output
       volumes:
         - name: spark-events
           emptyDir: {}
+        - name: spark-output
+          persistentVolumeClaim:
+            claimName: spark-analytics-output