export function exportToCsv(filename: string, rows: any[]) {
  if (!rows.length) return;
  const keys = Object.keys(rows[0]);
  const csv = keys.join(',') + '\\n' +
    rows.map(r => keys.map(k => JSON.stringify(r[k] || '')).join(',')).join('\\n');
  const blob = new Blob([csv], { type: 'text/csv' });
  const link = document.createElement('a');
  link.href = URL.createObjectURL(blob);
  link.download = filename;
  document.body.appendChild(link);
  link.click();
  link.remove();
}