fix(spark): disable service link env vars on master pod

K8s injects SPARK_MASTER_PORT=tcp://<ip>:7077 because the Service is
named spark-master. Spark master parses it as integer -> NumberFormatException.
enableServiceLinks: false suppresses all Docker-link style env var injection.

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

spark-cluster/base/master.yaml

@@ -16,6 +16,9 @@ spec:
         app.kubernetes.io/name: spark-master
         app.kubernetes.io/part-of: nowchess
     spec:
+      # Prevent K8s from injecting SPARK_MASTER_PORT=tcp://... env vars (Docker-link
+      # style). Spark master parses SPARK_MASTER_PORT as an integer and crashes.
+      enableServiceLinks: false
       containers:
         - name: spark-master
           image: apache/spark:4.0.3-scala2.13-java17-ubuntu