Banning rejoining accounts during Anti-Raid mode

Some spambots automatically rejoin after being kicked, leading to a lot of noise. Would it be possible (or practical) to be able to configure Anti-Raid Mode to ban people who rejoin x number of times?

Happy to look into a PR if requested.

Thanks

No files, tests, or entry points are named. Start by locating the Anti-Raid Mode implementation and the handling for users rejoining after a kick; determine how a configurable rejoin threshold should be stored and enforced, then verify that repeated rejoiners are banned without affecting ordinary joins.

Written by the indexing model from the issue text.