Pin github actions by sha

[yubiuser]

What does this PR aim to accomplish?:

Pins the actions used in our workflow by commit. This is the recommended way to prevent supply chain attacks

https://github.blog/changelog/2025-08-15-github-actions-policy-now-supports-blocking-and-sha-pinning-actions/

The human-friendly comment tag should be auto-updated by dependabot as well

https://github.blog/changelog/2022-10-31-dependabot-now-updates-comments-in-github-actions-workflows-referencing-action-versions/

Redone of #472 to resolve merge conflicts.

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