Add trading history CSV export

[Sikkra]

Closes #14.

Summary:

• Added a History toolbar CSV export action.
• Added an export modal with Last 7/30/90 days, all history, and custom date ranges.
• Fetches history in pages using the current status filters, formats rows with the existing history formatter, and downloads a CSV locally in the browser.
• Handles disconnected wallet state with a toast instead of exporting an empty report.

Verification:

• npm run build passes.

Note: local browser pointer verification is limited by the existing restricted-country overlay in this environment, but the build includes the modal and toolbar action successfully.