feat: add GitOps structure for kubernetes-dashboard, n8n, xslt-lab

- apps/kubernetes-dashboard: raw manifests (namespace, rbac, deployment, service, ingress)
- apps/n8n: Helm values referencing existing n8n-postgresql secret (no password in git)
- apps/xslt-lab: Helm values for xslt-playground chart
- argocd/applications: ArgoCD Application CRDs for all three apps

apps/kubernetes-dashboard/rbac.yaml

@@ -0,0 +1,18 @@
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: dashboard-admin
+  namespace: kubernetes-dashboard
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRoleBinding
+metadata:
+  name: dashboard-admin
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: ClusterRole
+  name: cluster-admin
+subjects:
+- kind: ServiceAccount
+  name: dashboard-admin
+  namespace: kubernetes-dashboard