Add tiered/layered server routing

Right now, the plugin simply denies a player if they try to go to a server. I'd like to suggest some more features, if possible. In my specific scenario, adding a routing layer would be helpful. Some way to say "if they don't have permission x, try y. if they don't have permission y, try z" and so on.

Velocity does have a "fallback server" option in the .toml. Maybe that could be implemented here? In my server, I have that fallback option set up where if the lobby fails, they get sent to vanilla, but that's not working with your plugin. It simply denies the login, whereas I'm wondering if it's possible to send them to vanilla (the fallback option after lobby) if they don't have the lobby permission, if that makes sense.

Look at the plugin's current server routing logic, likely in a class handling player connection or server switching. Understand how Velocity's fallback server configuration works. The goal is to implement a tiered routing system that checks permissions sequentially and falls back to a configured server. Test by setting up a Velocity proxy with the plugin and verifying players are routed correctly based on permissions.

Written by the indexing model from the issue text.