Implement drag-and-drop for file and image uploads

[latin-panda]

Description

Currently, Web Forms only supports manual file selection via the file explorer. We need to implement drag-and-drop functionality to improve the user experience across all upload interfaces.

• Edit coordinates dialog
• Upload image question type
• Upload file question type

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Checklist

• Does it need UI/UX design?
  • 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.
  • No
• Does it need design around state flow?
  • Yes. Outline the state flow requirements.
  • No
• Does it need a test plan?
  • Yes. Add the test plan as a comment in this task or attach the document.
  • No

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User Stories

• As a [user type],
  I want [functionality],
  so that [benefit].

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Design

• Figma: [Insert URL]
• Design Docs: [Insert URL]

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Dependencies

• File upload question type #370