ci: Node 20 → 24 deprecation across all workspace workflows

[mairas]

GitHub is forcing JavaScript actions still pinned to Node 20 onto Node 24 by default starting 2026-06-02. Node 20 is removed from runners on 2026-09-16. Surfaced today by a deprecation warning in `hatlabs/signalk-halpi` Main Branch CI/CD run (post-merge of hatlabs/signalk-halpi#15).

Affected actions seen so far:

• `actions/checkout@v4`
• `actions/setup-node@v4`
• `peter-evans/repository-dispatch@v3`

These are pulled in by virtually every workflow in the workspace, both directly and via `hatlabs/shared-workflows` + `halos-org/shared-workflows`.

Scope

Sweep `.github/workflows/` and `.github/actions/` across all workspace repos (both `halos-org` and `hatlabs`) and:

1. Audit which actions are still on Node 20.
2. Bump to a Node-24-capable version where one exists.
3. For actions without a Node-24 release yet, decide whether to opt-in early with `FORCE_JAVASCRIPT_ACTIONS_TO_NODE24=true` or wait for the action maintainer.
4. Run a representative workflow in each repo to confirm no regressions.

Why one umbrella issue

Many repos share workflow patterns through `shared-workflows`, and most fixes are one-line action-version bumps. Doing this once with a checklist and per-repo PRs avoids the same churn appearing in unrelated feature PRs over the next several weeks.

References

• Deprecation notice: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/
• Opt-in env var: `FORCE_JAVASCRIPT_ACTIONS_TO_NODE24=true`
• Temporary opt-out (post-default flip): `ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION=true`