Quickly combine multiple Factorio server-banlist.json files, removing duplicates.
Run QuickBanCombine file1.json file2.json ... to write composite.json.
Inputs can contain username strings or objects with username and reason.
Usernames are combined without regard to case across all files. Duplicate bans
are retained once, with distinct nonempty reasons joined under a [dup] prefix.
Invalid inputs stop processing before the existing output is replaced.