Feature Request: Export raffle winners to CSV, XLS, or JSON

[Spaccesi]

Summary

After a raffle, there's no way to export the list of winners for record-keeping or external processing.

Possible Solution

• Add an "Export Winners" button on the results screen.
• Let the user choose the format: .csv, .xlsx, or .json.
• Include draw timestamp, participant name, and position.

Acceptance Criteria

• Users can export winner results in at least one of the supported formats.
• Exported file includes winner name, position, and draw date/time.
• Export works on both Android and iOS (using share sheet where applicable).