Move to .env file for service configuration

[nuke-web3]

There are a few settings and keys required at startup time, ideally these would all be configurable in one way (with options to override a file with CLI or env vars).
https://github.com/allan2/dotenvy makes things a bit cleaner & easier to build on top of (especially for managing semi-secure keys in a ok way).

[S1nus]

Closing this since the PR is merged.

[nuke-web3]

I still want to bring in this dep, as otherwise one must remember to source .env or things fail.