Browser integration changes

This MR Downgrades some dependencies:

base64 v0.21
serde_with v3.0.0
thiserror v1
lox-zkp 0.8.0

Creates a bridgeauth feature in the lox-library that separates the server specific code out for client applications. I'm not certain I've done this in the best way but can iterate on these changes here before pushing to crates.io

//cc @pierov