monitoring(grafana): swap python3 for jq in folder-ACL local-exec

CI image (ci/Dockerfile) is alpine + jq, no python3. The
grafana_admin_only_folder_acl null_resource was parsing /api/folders
with a python3 oneliner, which crashed every CI apply with
"python3: command not found" and made every monitoring stack apply
fail in CI (worked locally because the dev VM has python3).

jq is already in the CI image and produces the same output.

stacks/monitoring/modules/monitoring/grafana.tf

@@ -196,7 +196,7 @@ resource "null_resource" "grafana_admin_only_folder_acl" {
       for i in $(seq 1 12); do
         FOLDER_UID=$(kubectl $KUBECONFIG_FLAG exec -n monitoring "$POD" -c grafana -- \
           curl -sf -u "admin:$ADMIN_PW" "http://localhost:3000/api/folders" \
-          | python3 -c "import json,sys; folders=json.load(sys.stdin); print(next((f['uid'] for f in folders if f['title']==sys.argv[1]), ''))" "$FOLDER" || true)
+          | jq -r --arg t "$FOLDER" 'first(.[] | select(.title == $t) | .uid) // ""' || true)
         if [ -n "$FOLDER_UID" ]; then break; fi
         sleep 5
       done