Switch to Material 3 theme

[seadowg]

This is mostly a dev facing change (although some things like Dialogs will update to newer styles). We want our app theme to extend Theme.Material3.DayNight.NoActionBar instead of Theme.MaterialComponents.DayNight.NoActionBar. This will mean that we don't have to explicitly add Material 3 styles or polyfill Material 3 attributes.

It will mean that some things in the app will start using the default Material 3 colours and so fixing that should be part of this.