Implement safe auto News role adding

Currently, Dyno gives all users the `@News` role at join, which unfortunately bypasses the required verification level on the server.

This should be disabled and a new feature created on TeX-Bot so that only users that meet the value verification level are given the role.

To do this, the member update event should be monitored and if `pending` has become false, give the user the news role.

https://docs.pycord.dev/en/stable/api/events.html#discord.on_member_update

Start by locating the existing join-time assignment of the @News role and the member update event handler. Read the linked Pycord on_member_update documentation, then verify the change by checking that the role is assigned only when pending becomes false and the existing automatic assignment is disabled.

Written by the indexing model from the issue text.