feat(vault): deploy HashiCorp Vault 2.0.1 via Helm chart (5-replica HA raft) (#148)

## Summary

- Deploys HashiCorp Vault 2.0.1 using Helm chart 0.32.0 in HA raft mode (5 replicas)
- Configuration modelled on production vault: \`disable_mlock=true\`, headless-DNS retry_join for all 5 pods
- IPC_LOCK capability added via \`server.statefulSet.securityContext.container\`
- 10Gi cephrbd-fast-delete PVC per pod via \`dataStorage\`
- Gateway API: HTTPS gateway + HTTPRoute (443→vault service port 8200) at \`vault.k8s.syd1.au.unkin.net\`
- ArgoCD platform ApplicationSet updated to include vault overlay path
- Injector disabled (no agent sidecar injection needed)

## Requires

- PR #147 (artifactapi: add hashicorp/vault to docker immutable patterns) to be merged first

## Test plan

- [ ] Sandbox tested in \`sandbox-vault\`: all 5 pods Running, raft cluster forming
- [ ] After merge: ArgoCD syncs vault namespace
- [ ] Operator runs \`vault operator init\` to initialize, then unseals all 5 nodes
- [ ] Verify \`vault.k8s.syd1.au.unkin.net\` is accessible via Gateway

Reviewed-on: #148

apps/overlays/au-syd1/traefik-system/values-internal.yaml

@@ -94,5 +94,7 @@ ports:
     port: 80
   websecure:
     port: 443
+  vault-direct:
+    port: 8200
 
 enabled: true

apps/overlays/au-syd1/vault/kustomization.yaml

@@ -0,0 +1,14 @@
+---
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+resources:
+  - ../../../base/vault
+
+helmCharts:
+  - name: vault
+    repo: https://helm.releases.hashicorp.com
+    version: "0.32.0"
+    releaseName: vault
+    namespace: vault
+    valuesFile: values.yaml

apps/overlays/au-syd1/vault/values.yaml

@@ -0,0 +1,73 @@
+server:
+  image:
+    repository: hashicorp/vault
+    tag: "2.0.1"
+
+  ha:
+    enabled: true
+    replicas: 5
+
+    raft:
+      enabled: true
+      setNodeId: true
+      config: |
+        ui            = true
+        disable_mlock = true
+
+        listener "tcp" {
+          address         = "[::]:8200"
+          cluster_address = "[::]:8201"
+          tls_disable     = "true"
+        }
+
+        storage "raft" {
+          path = "/vault/data"
+
+          retry_join {
+            leader_api_addr = "http://vault-0.vault-internal.vault.svc.cluster.local:8200"
+          }
+          retry_join {
+            leader_api_addr = "http://vault-1.vault-internal.vault.svc.cluster.local:8200"
+          }
+          retry_join {
+            leader_api_addr = "http://vault-2.vault-internal.vault.svc.cluster.local:8200"
+          }
+          retry_join {
+            leader_api_addr = "http://vault-3.vault-internal.vault.svc.cluster.local:8200"
+          }
+          retry_join {
+            leader_api_addr = "http://vault-4.vault-internal.vault.svc.cluster.local:8200"
+          }
+        }
+
+        service_registration "consul" {
+          address = "consul-server.consul.svc.cluster.local:8500"
+        }
+
+  dataStorage:
+    enabled: true
+    size: 10Gi
+    storageClass: cephrbd-fast-delete
+    accessMode: ReadWriteOnce
+
+  statefulSet:
+    securityContext:
+      container:
+        capabilities:
+          add:
+            - IPC_LOCK
+
+  resources:
+    requests:
+      memory: 256Mi
+      cpu: 100m
+    limits:
+      memory: 2Gi
+      cpu: 1000m
+
+injector:
+  enabled: false
+
+ui:
+  enabled: true
+  serviceType: ClusterIP