Output sie accounting as cp437 encoding instead of UTF8

[nitro2k01]

The SIE format mandates cp437 encoded data, which means account names are mangled in the import.

I did a quick test by iconving the current exported format to cp437 and it removes the conflicts. (Other than accounts that are currently named wrong.)

iconv -f UTF8 -t CP437 /home/nitro2k01/Downloads/2025-09-01_2025-10-01_month.si -o /home/nitro2k01/Downloads/2025-09-01_2025-10-01_month_cp437.si

Before:

After: