Add download button to file upload widget

### Description

Give users a way to download or preview a file.

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### Checklist
- **Does it need UI/UX design?**
- [x] Yes. Describe the UI/UX requirements or attach a Figma link in the "Design" section.
- [ ] No
- **Does it need API design?**
- [ ] Yes. Specify the endpoints, methods, or data structures needed.
- [x] No
- **Does it need design around state flow?**
- [ ] Yes. Outline the state flow requirements.
- [x] No
- **Does it need a test plan?**
- [ ] Yes. Add the test plan as a comment in this task or attach the document.
- [x] No
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### User Stories

- **As a** form filler,
**I want** to be able to confirm I've uploaded the right file,
**so that** the right file is uploaded.

- **As a** form editor,
**I want** to be able to view the uploaded file,
**so that** I can confirm the details that were submitted.

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### Design

- **Figma**: [Insert URL]
- **Design Docs**: [Insert URL]

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### Dependencies

-

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### Additional Notes

-

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### Related Issues

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No file, test, or entry point is named; start by locating the file upload widget and reviewing how uploaded files are represented and displayed. Clarify the missing Figma or design documentation, then define whether the completed feature must support download, preview, or both and verify that users can confirm the uploaded file.

Written by the indexing model from the issue text.