Invite tracker

The Invite tracker module in AscensionBot — what it does and how to configure it.

On every join, the bot diffs every invite code's use count against its last known state to figure out exactly which link was used — no guessing, no third-party dependency. `/invite stats` shows anyone's recruiting count, `/invite leaderboard` ranks your top inviters, and `/invite check` reveals who invited a specific member. Perfect for partner programs, recruitment contests, or just seeing where your community actually comes from.