feat(security): add Kyverno for image scanning and Pod security policies

- Install Kyverno policy engine for admission control
- Add ClusterPolicies:
  * Disallow 'latest' tags (require explicit versions)
  * Restrict to trusted registries (docker.io, ghcr.io, quay.io, etc.)
  * Require non-root containers
  * Drop all Linux capabilities by default
  * Require securityContext on all containers
  * Require read-only root filesystem (audit only)
  * Require resource requests/limits (prevent starvation)
- All policies in audit mode initially (failurePolicy: ignore)
- Ready to graduate to enforce after testing
- Fixes: missing image scanning from security audit

k8s/argocd/apps/00-substrate.yaml

@@ -159,3 +159,54 @@ spec:
     automated:
       prune: true
       selfHeal: true
+---
+apiVersion: argoproj.io/v1alpha1
+kind: Application
+metadata:
+  name: kyverno
+  namespace: argocd
+  annotations:
+    argocd.argoproj.io/sync-wave: "0"
+spec:
+  project: homelab
+  source:
+    repoURL: https://kyverno.github.io/kyverno/
+    chart: kyverno
+    targetRevision: "1.14.0"
+    helm:
+      valueFiles:
+        - $values/k8s/bootstrap/kyverno/kyverno-values.yaml
+  sources:
+    - repoURL: https://forgejo.riotpiao.com/rock/homelab.git
+      targetRevision: main
+      ref: values
+  destination:
+    server: https://kubernetes.default.svc
+    namespace: kyverno
+  syncPolicy:
+    automated:
+      prune: true
+      selfHeal: true
+    syncOptions:
+      - CreateNamespace=true
+---
+apiVersion: argoproj.io/v1alpha1
+kind: Application
+metadata:
+  name: kyverno-policies
+  namespace: argocd
+  annotations:
+    argocd.argoproj.io/sync-wave: "0"
+spec:
+  project: homelab
+  source:
+    repoURL: https://forgejo.riotpiao.com/rock/homelab.git
+    targetRevision: main
+    path: k8s/bootstrap/kyverno
+  destination:
+    server: https://kubernetes.default.svc
+    namespace: kyverno
+  syncPolicy:
+    automated:
+      prune: true
+      selfHeal: true