fix: recompute all sha hashes

[wolfv]

Description

Our aggregated SHA file and the dist-*.json file was still not correct. This should recompute the hashes before pushing them to the release.

This will all go away once we move to the new release workflow from rattler-build.

How Has This Been Tested?

Not yet, need to dry-run.

AI Disclosure

Tools: Claude

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added sufficient tests to cover my changes.
• I have verified that changes that would impact the JSON schema have been made in schema/model.py.

[ruben-arts]

Please we can merge this so you can test it. But please do that before we hold back another release because of it!

[wolfv]

Yes, let's merge and dry run? I can check the artifacts then

[ruben-arts]

@wolfv I started it for you here: https://github.com/prefix-dev/pixi/actions/runs/23237139204