Inject service account spec to Aggregator

```
Caller does not have storage.objects.list access to the Google Cloud Storage bucket. Permission 'storage.objects.list' denied on resource (or it may not exist).
```

Author: linamy85

Ironwood/guides/automation/aggregator.yaml

@@ -3,8 +3,10 @@ kind: Job
 metadata:
   name: aggregator
 spec:
+  backoffLimit: 0
   template:
     spec:
+      serviceAccountName: ${GCS_SA_NAME}
       containers:
       - name: main-app
         image: python:3.12

Ironwood/guides/automation/automation_launch.sh

@@ -209,9 +209,12 @@ echo ""
 echo "Jobs completed. Aggregating results..."
 echo ""
 
-envsubst '${GCS_BUCKET_ROOT_DIR}' < ${SCRIPT_DIR}/aggregator.yaml | kubectl apply -f -
+# Ensure cleanup of any previous aggregator job to avoid immutable field errors
+kubectl delete job aggregator --ignore-not-found=true
+
+envsubst '${GCS_BUCKET_ROOT_DIR} ${GCS_SA_NAME}' < ${SCRIPT_DIR}/aggregator.yaml | kubectl apply -f -
 wait_for_job_completion "aggregator" ${TIMEOUT_SECOND}
-envsubst '${GCS_BUCKET_ROOT_DIR}' < ${SCRIPT_DIR}/aggregator.yaml | kubectl delete -f -
+envsubst '${GCS_BUCKET_ROOT_DIR} ${GCS_SA_NAME}' < ${SCRIPT_DIR}/aggregator.yaml | kubectl delete -f -
 
 # Print the failed jobs at the end for better visibility.