We have our base images, and in there we install dependencies by version. That package then is the base for our code build. (as apt seemingly doesn't have any lock file support?).
In the subsequent built EVERYTHING is versioned, which allows us to establish provenance all the way up to the base image.
And next to that when we promote images from PR -> main we don't even rebuild the code. It's the same image that gets retagged. All in the name of preserving provenance.