support .env.local for hasura CLI

Hasura CLI currently only looks for environment varables like `HASURA_GRAPHQL_ADMIN_SECRET ` from `.env`
Traditionally we keep local development-specific environment variables in ` .env.local` (added to .gitignore)
It would be nice if Hasura CLI override environment variables from ` .env.local` as well.

Start at the Hasura CLI entry point that loads variables from `.env`, then inspect how `.env.local` would be discovered and how precedence is handled. Look for existing environment-loading tests or commands to run; done means local values are loaded and override matching `.env` values without changing other behavior.

Written by the indexing model from the issue text.