Create a better auth error page

[definitelynobody]

While authentication errors should be less common #182 we should still handle them in a more user friendly way.

Instead of giving people a string error and no navigation here:

benefice/src/auth/mod.rs

Line 80 in 6117098

fn ice<E: std::fmt::Debug>(info: &'static str) -> impl Fn(E) -> (StatusCode, &'static str) {

The user currently sees this when errors are handling in this way:

Users should have the ability to retry the login or navigate the homepage as normal and should be presented with a less confusing error message.