Add PriorityClass, ArgoCD jenkins-ci token, and Harbor robot secretstores

extra-manifests/priorityclass-high-priority.yaml: cluster-side
PriorityClass backing the app chart's hardcoded priorityClassName.
secretstores/argocd-jenkins-ci-token.yaml: ExternalSecret for the
scoped ArgoCD account devops-lib's syncArgoApp stage authenticates
with.
secretstores/harbor-robot-dockerconfig.yaml: ExternalSecret building a
dockerconfigjson from the Harbor robot account for image pulls.

extra-manifests/priorityclass-high-priority.yaml

@@ -0,0 +1,13 @@
+# devops-helm-charts' generic app chart (1.0.0, in templates/deployment.yaml)
+# hardcodes `priorityClassName: high-priority` on every Deployment it
+# renders — no values toggle, unconditional. No such PriorityClass exists
+# on this cluster, and a Pod referencing a nonexistent one gets hard-
+# rejected by the API server at admission, not soft-failed. Simplest fix:
+# just create it, rather than fork the chart's own template.
+apiVersion: scheduling.k8s.io/v1
+kind: PriorityClass
+metadata:
+  name: high-priority
+value: 1000
+globalDefault: false
+description: "For app workloads deployed via devops-helm-charts' generic chart, which hardcodes this class name."