add buckets to storage regions repo types

[julien-c]

buckets are now covered by storage regions alongside models datasets and Spaces

disclaimer: my julien-cto agent helped me write this

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Note

Low Risk
Documentation-only wording changes with no product or code impact.

Overview
Updates Storage Regions docs so buckets are listed alongside models, datasets, and Spaces as org resources whose region can be chosen.

The intro paragraph and the EU GDPR compliance example now mention buckets (and inference endpoints in the compliance line) as stored in the selected region.

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[HuggingFaceDocBuilderDev]

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