Improve environment variable handling and reading (#5389)

* wip: better env var reading

* move most env vars to env.rs

* migrate more env vars

* more migration

* more migrations

* More migration

* 🦀 dotenvy is gone (almost)

* 🦀 dotenvy is gone 🦀

* Fix mural source account env var handling

* Remove defaults from admin key vars

* dummy commit to update github pr

* fix ci

apps/labrinth/src/util/mod.rs

@@ -6,7 +6,6 @@ pub mod bitflag;
 pub mod captcha;
 pub mod cors;
 pub mod date;
-pub mod env;
 pub mod error;
 pub mod ext;
 pub mod gotenberg;