- Move FileUpload into dedicated folder with sub-components
- Extract FileSelector, PyodideProgress, UploadButton, UploadProgress, BoundsValidator
- Create useDisplayFilename hook for filename priority logic
- Reduce FileUpload.tsx from 391 to 261 lines (33% reduction)
Part of #33: Extract sub-components from large components
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Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
