feat: migrate vso-system to ArgoCD (#81)

Migrate Vault Secrets Operator from Terragrunt to ArgoCD/Kustomize.
Deploys vault-secrets-operator v1.2.0 with 3 replicas, plus ClusterRole,
ClusterRoleBindings, and vault-admin ServiceAccount.

Note: static service account tokens (kubernetes.io/service-account-token)
cannot be stored in git; create manually or via Vault after deployment.

💘 Generated with Crush

Assisted-by: Claude Sonnet 4.6 via Crush <crush@charm.land>

Reviewed-on: #81

apps/overlays/au-syd1/vso-system/kustomization.yaml

@@ -0,0 +1,24 @@
+---
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+namespace: vso-system
+
+resources:
+  - ../../../base/vso-system
+
+helmCharts:
+  - name: vault-secrets-operator
+    repo: https://helm.releases.hashicorp.com
+    version: "1.2.0"
+    releaseName: vault-secrets-operator
+    namespace: vso-system
+    valuesFile: values.yaml
+
+patches:
+  - path: patch_vaultauth-remove-namespace.yaml
+    target:
+      group: secrets.hashicorp.com
+      version: v1beta1
+      kind: VaultAuth
+      name: default

apps/overlays/au-syd1/vso-system/patch_vaultauth-remove-namespace.yaml

@@ -0,0 +1,2 @@
+- op: remove
+  path: /spec/namespace

apps/overlays/au-syd1/vso-system/values.yaml

@@ -0,0 +1,28 @@
+defaultVaultConnection:
+  enabled: true
+  address: "https://vault.service.consul:8200"
+  skipTLSVerify: false
+  caCertSecret: "vault-ca-cert"
+
+defaultAuthMethod:
+  enabled: true
+  method: "kubernetes"
+  mount: "k8s/au/syd1"
+  namespace: ""
+  kubernetes:
+    role: "default"
+    serviceAccount: "vault-secrets-operator-controller-manager"
+    tokenAudiences: ["vault"]
+
+controller:
+  replicas: 3
+  resources:
+    limits:
+      cpu: 500m
+      memory: 256Mi
+    requests:
+      cpu: 50m
+      memory: 128Mi
+
+globalVaultAuth:
+  enabled: true