Improve .env setup

[SebastienGllmt]

Currently, the .env file contains two lines that aren't proper .env syntax:

SOCKET="$(realpath ../cardano-node/bin/\\.pipe\\cardano-node)"
PGPASSFILE="$(realpath secrets/.pgpass)"

The fact we have these is unfortunate because it means you can't just load the dotenv from inside Rust (or Typescript) and instead have to set the env variables by calling the .env through bash.