Use library to handle config, envs and cli args all at once

We could use a library like [config](https://github.com/num30/config) to handle config, envs and cli args all at once declaratively.

This should also remove the need of the `usage.go` module

_Originally posted by @sanzoghenzo in https://github.com/pyrevitlabs/telemetry-server/pull/1#discussion_r2120548655_
            