[DSO-1278] Bump GitHub Actions versions

[wf-swarm]

Summary

Bumps third-party GitHub Actions referenced in DSO-1278 to their target major versions:

• `1password/load-secrets-action`: `v1.3.1` → `v4` (the issue tracked it as `v3` → `v4`; the workflow was actually pinned to `v1.3.1`, bumped to the target `v4` regardless)
• `actions/cache`: `v3` → `v5`

Affects both `actions-publish.yml` and `actions-test.yml`.

Notes

• The `Repo:` line in the Linear issue uses lowercase (`repo:`), so the workspace `after_create` hook did not auto-clone — bootstrapped manually this turn.
• `actions/checkout@v3` is not mentioned in the issue scope, left as-is.

Linear: DSO-1278

[wf-swarm]

Squashed into a single commit. Audited all workflow files against the full list — the three actions present in the codebase were already updated to target versions:

• actions/checkout: v3 → v6 ✓
• actions/cache: v3 → v5 ✓
• 1password/load-secrets-action: v1.3.1 → v4 ✓

None of the other actions in the list (e.g. 1password/install-cli-action, actions/setup-node, docker/setup-buildx-action, etc.) appear in any workflow file in this repo.