feat(csv-export): add gas fee columns to transaction history CSV export

[falvaradorodriguez]

• Closes https://linear.app/safe-global/issue/PLA-1419/history-csv-export-should-contain-paid-from-the-safe-info#comment-9b93eec1

• Related with https://github.com/safe-global/safe-transaction-service/pull/2878/changes

  Summary

  • Adds gasToken, fee, gasTokenSymbol and gasTokenDecimals fields
    to TransactionExportSchema, parsing the new fields returned by the Tx Service
    /api/v1/safes/{address}/export/ endpoint (PLA-1419)
  • Formats the raw fee amount using formatUnits(fee, gasTokenDecimals),
    matching the existing pattern for amount/assetDecimals
  • Adds two new columns to the CSV output: "Amount Gas" and "Gas token";
    both are empty when the fee was paid from the signer wallet (fee is null)