Add more message deletion options and fix the 'ban to not delete messages' vulnerability for users

When you get banned or kicked from a server, you cannot delete your messages sent in there, only the moderators. This is the exact same issue as discord, you send a revealing message and then a mod bans you so they can use the message/screenshot it, etc. Zero control whether every other message also gets deleted

When you get banned or kicked from a server, you should get a popup saying you were banned from said server and an option to delete all your messages from it (requires your password, just like leaving a server and deleting all your messages from it too)