Add pnpm store cache to runner via persistent Docker volume

Mount a named Docker volume (pnpm-store) into every job container
at the default pnpm store path. The volume persists in the DinD
sidecar across job runs, so pnpm install reuses cached packages.

infra/kubernetes/platform/gitea-runner/kustomization.yaml

@@ -2,4 +2,5 @@ apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 resources:
   - deployment.yaml
+  - runner-config.yaml
   - gitea-runner-token-sealed.yaml