Moved default SSH keys to a shared `common.nix` module for better reusability and maintainability. Updated references in both NixOS and Darwin user modules to use the centralized keys. This reduces redundancy and improves consistency across modules.
Changed the neovim-flake URL to the new repository and updated its version from v0.5 to v0.6. This ensures we are using the latest configurations and features from the renamed repository.
Harald Hoyer