Replace config crate with Figment

Config is not maintained anymore and should be replaced with another crate, for example https://github.com/SergioBenitez/Figment

Start by locating where the `config` crate is declared and used in the CLI, then review Figment's configuration model and assess the replacement scope. No files or tests are named in the issue; done means the unmaintained `config` crate has been replaced by Figment without leaving its existing usage unresolved.

Written by the indexing model from the issue text.