Remove API documentation infrastructure

[mathemancer]

Fixes #3540

This removes the DRF Spectacular dependency and all parts of the codebase directly related to OpenAPI documentation generation.

Checklist

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  visible errors.

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[mathemancer]

Blocked until #3538 is merged.

[mathemancer]

@Anish9901 Should be able to review this. I based it off of the demo code removal to make the changes more obvious.