[#188] Remove outdated Nix configurations for frontend

Removed obsolete Nix configuration files (default.nix, node-env.nix, and
node-packages.nix) from the frontend module. This change is part of a
broader effort to update and realign the frontend's build and deployment
process with the backend's, ensuring a more streamlined and optimized
development environment. The removal of these files paves the way for
introducing a revised and more efficient Nix setup that better mirrors
the backend's configuration and fulfills the specified acceptance
criteria for development environments and dependencies.