feat: CSV export for account transaction history

[dannywillems]

Summary

Add the ability to export an account's transaction history as a CSV file, with optional date range filtering.

Use Case

Users need to download transaction data for specific accounts for:

• Tax reporting and accounting
• Analyzing transaction patterns
• Importing into spreadsheets or other tools
• Record keeping

Requirements

Data to Include

• Transaction hash
• Type (sent/received/zkApp)
• Counterparty address
• Amount (in MINA)
• Fee (in MINA)
• Timestamp (ISO 8601)
• Block height
• Memo (if present)
• Status (confirmed/pending)

Filtering Options

• Date range picker (from/to)
• Preset ranges: Last 7 days, 30 days, 90 days, All time
• Transaction type filter (sent/received/all)

UI Location

• Account detail page (/account/:publicKey)
• Add "Export CSV" button near the transactions table
• Show export options in a dropdown or modal

CSV Format Example

hash,type,counterparty,amount,fee,timestamp,block_height,memo,status
5Jt...,sent,B62q...,100.5,0.01,2025-01-15T10:30:00Z,508500,Payment,confirmed
5Ju...,received,B62r...,50.0,0.01,2025-01-14T08:15:00Z,508450,,confirmed

Technical Notes

• Use existing fetchAccountTransactions API
• Consider pagination for large exports (may need to fetch in batches)
• Generate CSV client-side using a library or native JS
• Include BOM for Excel compatibility with UTF-8

Acceptance Criteria

• Export button visible on account detail page
• Date range filter works correctly
• CSV downloads with correct filename (e.g., transactions_B62q...abc_2025-01-15.csv)
• All transaction types included
• Handles accounts with no transactions gracefully
• Works on both desktop and mobile