feat(phase0): bootstrap External Secrets Operator and fix helmfile dual-ownership

Phase 0 groundwork for helmfile→ArgoCD migration:

1. Remove 3 bootstrap releases from helmfile (cert-manager, reloader, ingress-nginx)
   — already managed by terraform/bootstrap-releases.tf; eliminates dual-ownership

2. Bootstrap ESO (External Secrets Operator) as TF-managed release
   — required for all ExternalSecret resources in phases 1-3
   — added to bootstrap-releases.tf + helm-repositories.tf

3. Create ClusterSecretStore connecting ESO to Vault (K8s auth)
   — enables per-namespace/per-release secret injection
   — vault config documented in docs/PHASE0-ESO-VAULT-SETUP.md (manual setup)

4. Fix argocd-bootstrap.tf CA cert copy: use jq instead of sed for cleaner metadata handling

Changes:
- helmfile.yaml.gotmpl: remove cert-manager/reloader/ingress-nginx blocks
- terraform/bootstrap-releases.tf: add external-secrets release
- terraform/helm-repositories.tf: add external-secrets Helm repo
- k8s/external-secrets/clustersecretstore.yaml: ESO→Vault ClusterSecretStore
- k8s/argocd/apps/0-wave-0.yaml: stub wave 0 applications (schema fix, rewrite pending Phase 1)
- docs/PHASE0-ESO-VAULT-SETUP.md: manual ESO-Vault auth setup procedure

Next: Phase 1 will incrementally rewrite ArgoCD Applications + migrate helmfile releases.

Co-Authored-By: Claude Haiku 4.5 <[email protected]>

k8s/external-secrets/clustersecretstore.yaml

@@ -0,0 +1,19 @@
+# ClusterSecretStore — ESO's connection to Vault
+# References the Vault instance deployed in the iam namespace.
+# Uses Kubernetes auth method (safe for in-cluster access).
+# Namespace: default (ClusterSecretStore is cluster-scoped, not namespaced).
+
+apiVersion: external-secrets.io/v1beta1
+kind: ClusterSecretStore
+metadata:
+  name: vault-homelab
+spec:
+  provider:
+    vault:
+      server: "http://vault.iam.svc.cluster.local:8200"
+      path: "secret"
+      version: "v2"
+      auth:
+        kubernetes:
+          mountPath: "kubernetes"
+          role: "external-secrets"