Add terraform-rancher woodpecker ServiceAccount (#257)

## Why

The new terraform-rancher CI pipeline runs as a pod in the woodpecker namespace; its ServiceAccount token is what Vault binds to the `woodpecker_terraform_rancher` k8s auth role (see terraform-vault#86) for rancher2 provider auth + Consul state.

## Change

- Add `ServiceAccount/terraform-rancher` (woodpecker ns) and wire it into the woodpecker kustomization, mirroring the other terraform-* runner SAs.

## Validation

`kustomize build apps/base/woodpecker` renders it; pre-commit clean.

Reviewed-on: #257
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>

apps/base/woodpecker/kustomization.yaml

@@ -10,6 +10,7 @@ resources:
   - serviceaccount_terraform_authentik.yaml
   - serviceaccount_terraform_git.yaml
   - serviceaccount_terraform_prowlarr.yaml
+  - serviceaccount_terraform_rancher.yaml
   - serviceaccount_terraform_radarr.yaml
   - serviceaccount_terraform_sonarr.yaml
   - serviceaccount_terraform_vault.yaml

apps/base/woodpecker/serviceaccount_terraform_rancher.yaml

@@ -0,0 +1,6 @@
+---
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: terraform-rancher
+  namespace: woodpecker