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/deployment.yaml

@@ -0,0 +1,42 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: kubernetes-dashboard
+  namespace: kubernetes-dashboard
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      k8s-app: kubernetes-dashboard
+  template:
+    metadata:
+      labels:
+        k8s-app: kubernetes-dashboard
+    spec:
+      serviceAccountName: dashboard-admin
+      containers:
+      - name: kubernetes-dashboard
+        image: kubernetesui/dashboard:v2.7.0
+        imagePullPolicy: IfNotPresent
+        args:
+        - --auto-generate-certificates
+        ports:
+        - containerPort: 8443
+        livenessProbe:
+          httpGet:
+            path: /
+            port: 8443
+            scheme: HTTPS
+          initialDelaySeconds: 30
+          timeoutSeconds: 30
+        securityContext:
+          allowPrivilegeEscalation: false
+          readOnlyRootFilesystem: true
+          runAsNonRoot: true
+          runAsUser: 1001
+        volumeMounts:
+        - mountPath: /tmp
+          name: tmp-volume
+      volumes:
+      - name: tmp-volume
+        emptyDir: {}