Replaces Consul service registration with the native Kubernetes provider so Vault labels its own pods with active/standby/perf-standby status without requiring a Consul dependency.
## Changes
- `values.yaml`: swap `service_registration "consul"` for `service_registration "kubernetes" {}`, add `VAULT_K8S_NAMESPACE` and `VAULT_K8S_POD_NAME` env vars via downward API
- `role_k8s-service-registration.yaml`: Role + RoleBinding granting the `vault` service account `get`/`update`/`patch` on pods
- `kustomization.yaml`: include new RBAC file
Reviewed-on: #171
## 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
unkinben