fix: move from devenv to nix flake and add test for environment with quotes

documentation/manual/de/book/theme-tomorrow_night.js

documentation/manual/de/book/tomorrow-night.css

documentation/manual/de/mdbook-admonish.css

documentation/manual/de/mermaid-init.js

documentation/manual/de/mermaid.min.js

documentation/manual/de/source/01-Einleitung.md

documentation/manual/de/source/02-Erste-Schritte.md

documentation/manual/de/source/404.md

documentation/manual/de/source/SUMMARY.md

documentation/manual/de/source/imprint.md

documentation/manual/de/theme/book.js

env.go

env_test.go

export.go

file.go

flake.lock

flake.nix

go.mod

http-handler_test.go

import.go