feat: pre-install docker in node-runner image

- Dockerfile.node extends node:22-bookworm with docker.io
- No need for install step in every workflow
- Values-node.yaml references custom image
- Build and push manually (no CI needed)

k8s/infra/forgejo-runner/values-node.yaml

@@ -6,7 +6,8 @@
 # (homelab has no CI; custom runner images built manually if desired)
 runner:
   name: node-runner
-  labels: "node:docker://node:22-bookworm"
+  # Custom image: node:22-bookworm + docker.io pre-installed
+  labels: "node:docker://forgejo.riotpiao.com/rock/forgejo-runner-node:latest"
 
 # GC CronJob renders only from the default (golang) values to avoid duplicates
 gc: