## Summary
- Add `containers/nettest/default.nix` using `dockerTools.buildLayeredImage` with curl, jq, dnsutils, cacert, and bash — equivalent to the existing Dockerfile
- Update `container-tag-and-release` to require `--nix` or `--dockerfile` flag when both build types exist for a container
- Update `container-list` to show `[dockerfile+nix]` label when both exist
## Deployment and Testing
- [ ] SSH to ringtail, run `nix build -f containers/nettest/default.nix -o result` to verify the nix expression builds
- [ ] Tag `nettest-nix-v1.0.0`, confirm `build-container-nix` workflow runs on `nix-container-builder` runner and pushes to registry
- [ ] Smoke test on ringtail k3s: `kubectl run nettest --image=registry.ops.eblu.me/blumeops/nettest:v1.0.0 --restart=Never && kubectl logs nettest`
- [ ] Verify `mise run container-list` shows `[dockerfile+nix]` for nettest
- [ ] Verify `mise run container-tag-and-release nettest v1.1.0` prompts for build type
Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/214
Erich Blume
695089499e