Replaces nerdfonts.override with specific nerd-fonts packages for FiraCode, JetBrainsMono, and Iosevka in desktop and laptop configurations. Also corrects PulseAudio configuration by enabling it under services.pulseaudio instead of hardware.pulseaudio in common.nix.
Add a NixOS system configuration using flakes, supporting multiple hosts (desktop, laptop, my-machine) with shared and per-host settings. Includes Home Manager integration, user-level and system-level package management, and example hardware configuration placeholders. Provides a README with setup instructions and a .gitignore for common Nix and editor artifacts.
