fix: add black so our AI dev platform formats correctly

[astuyve]

What does this PR do?

Our internal vibecoding platform couldn't properly format my previous PR because black is used in check_format.sh but not anywhere in our pyproject.toml file.

Now you can actually use the same formatter we use in CI.

Should I probably also update the script so we don't pin a version of black there?

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• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

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