feat: add kubeadm bootstrap, Argo CD root app and lab RBAC

Terraform 설계서 7.2·7.3의 WP-07 내용.

- bootstrap/kubeadm/init-cp.sh: kubeadm init(사설 IP advertise, EIP cert SAN,
  pod CIDR 10.244.0.0/16) → flannel v0.28.9 → Argo CD v3.5.3(server-side apply)
  → root-app 적용 → 워커 join 명령을 /opt/selfheal/join.sh(0600)에 저장. 재실행 안전.
- bootstrap/kubeadm/join-worker.sh: join 명령을 stdin으로 받아 실행(토큰이 터미널·로그에
  남지 않음). 이미 join된 노드는 0으로 종료.
- argocd/root-app.yaml: apps/ 재귀 app-of-apps(공개 저장소, 자격증명 불요).
- apps/rbac.yaml + workloads/rbac: 네임스페이스 chaos-mesh·demo, SA harness(ClusterRole
  selfheal-harness: chaos-mesh.org/*, deployments·scale, pods, nodes patch, pods/eviction),
  SA ai-reader(ClusterRole view).

bootstrap/kubeadm/join-worker.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+# Worker join (Terraform design 7.2). Feed the join command produced on the CP through stdin, from the operator host:
+#   ssh -i ~/.ssh/selfheal-lab ubuntu@<CP_EIP> 'sudo cat /opt/selfheal/join.sh' \
+#     | ssh -i ~/.ssh/selfheal-lab -J ubuntu@<CP_EIP> ubuntu@<worker private ip> 'sudo bash /opt/selfheal/gitops/bootstrap/kubeadm/join-worker.sh'
+# The token never touches the operator terminal or a log. Safe to re-run: a joined node exits 0.
+set -euo pipefail
+if [ -f /etc/kubernetes/kubelet.conf ]; then echo "already joined"; exit 0; fi
+JOIN="$(cat)"
+case "$JOIN" in kubeadm\ join*) ;; *) echo "stdin is not a kubeadm join command" >&2; exit 1;; esac
+# shellcheck disable=SC2086
+$JOIN --node-name "$(hostname)"
+echo "joined"