fix: Make user loading case-insensitive
The archweb user export is case-sensitive while the config loading is case insensitive as per it's documentation:
Note also that keys in sections are case-insensitive and stored in lowercase.
As a consequence this makes the vote verification fail due to case mismatch.
$ make verify CONFIG=conf/mediator-team-2024.ini
<_io.TextIOWrapper name='conf/mediator-team-2024.ini' mode='r' encoding='UTF-8'>: invalid user name: antiz
$ grep -i antiz conf/all-users.csv
Antiz,Robin Candau,antiz@archlinux.org,262A58EC6C51F7EA395B2E2DFDC3040B92ACA748
Signed-off-by: Christian Heusel christian@heusel.eu