fix(ci): align nixfmt version and add statix/deadnix to CI

CI was using nixfmt-rfc-style while local tooling uses nixfmt-classic,
causing formatting mismatches. Also add statix and deadnix so linting
hooks actually run in CI instead of being silently skipped.

Author: svnlto

.github/workflows/pre-commit.yml

@@ -28,7 +28,7 @@ jobs:
       - name: Install Dependencies with Nix
         run: |
           # Install all dependencies via Nix
-          nix profile install nixpkgs#pre-commit nixpkgs#nixfmt-rfc-style nixpkgs#shellcheck
+          nix profile install nixpkgs#pre-commit nixpkgs#nixfmt-classic nixpkgs#statix nixpkgs#deadnix nixpkgs#shellcheck
 
       - name: Run pre-commit hooks
         run: |