* Add experimental flake.nix for NixOS/Linux development
This adds an experimental flake-based development environment and package entry for ArtCraft Launcher.
What this adds:
- `flake.nix` at the repository root
- Rust toolchain via `rust-overlay`
- Required native Linux libraries for the Rust workspace
- A dev shell via `nix develop`
- A package/app target via `nix run` / `nix build`
Why:
ArtCraft Launcher is a Rust workspace and currently has no Nix flake support. This makes local development and installation much easier for NixOS/Linux users.
Notes:
- This is intentionally minimal and experimental.
- It targets the development environment and local package use.
- Additional refinements may be needed for specific Wayland/X11 setups.
* Fix flake metadata to match ArtCraft Launcher and remove GTK dependency
* add flake.lock
* Update flake.nix: replace deprecated xorg packages with their new names
