file_name = 'ほげほげ.xlsx'
response['Content-Disposition'] = f'attachment; filename={file_name}'
↓↓↓↓
import urllib.parse
…
file_name = 'ほげほげ.xlsx'
file_name = urllib.parse.quote(file_name)
response['Content-Disposition'] = f'attachment; filename={file_name}; filename*=UTF-8{file_name}'