Wordlist feature: Consider user "new" until something is posted

Hi, I'm setting up Mjolnir and the `wordlist` protection seems to only support a time-based system for considering users as "new". New users will get banned automatically for posting certain terms (and presumably their message deleted), but unless we want to ban old users who happen to say a "bad" word the bot has to know who to trust. The problem is that we see bots joining many days before posting something that will get them banned. They just sit there in the room, waiting silently, then out of nowhere start spamming the channel. What I'd like is to have a user be considered as "new" until they post something. Better yet make the `minutesBeforeTrusting` mean "minutes after first message before trusting".

This would hopefully help a great deal in getting bots banned.

Start by locating the wordlist protection and its minutesBeforeTrusting setting, then trace how a user's first message affects trust. Done means users remain treated as new until they post, with the configured delay measured from that first message, while existing protection behavior remains intact.

Written by the indexing model from the issue text.