Add terraform-enc auth, consul state role, and encapi token grant

The new terragrunt-enc repo manages all encapi ENC data via Terraform and
needs its own Vault/Consul plumbing, mirroring terraform-git/terraform-incus:
CI auth, isolated consul state, and read access to the ENCAPI_WRITE_TOKEN.

- Add approle role terraform_enc and k8s auth role woodpecker_terraform_enc
  (bound to the terraform-enc SA in the woodpecker namespace).
- Add consul secret backend role + ACL rules granting write on
  infra/terraform/enc/ for its terragrunt state, plus a policy letting both
  auth roles read consul_root/au/syd1/creds/terraform-enc.
- Grant both auth roles read on
  kv/data/kubernetes/namespace/encapi/default/environment (ENCAPI_WRITE_TOKEN).

config/auth_kubernetes_role/k8s/au/syd1/woodpecker_terraform_enc.yaml

@@ -0,0 +1,7 @@
+bound_service_account_names:
+  - terraform-enc
+bound_service_account_namespaces:
+  - woodpecker
+token_ttl: 600
+token_max_ttl: 600
+audience: https://kubernetes.default.svc.cluster.local