refactor: implement component-based architecture for enhanced maintainability

- Reorganize directory structure into core/, features/, and themes/
- Colocate application Nix logic, configs, scripts, and theme overrides
- Implement 'Inversion of Control' for theming: apps now pull theme-specific layouts
- Update flake.nix and shared library paths to match the new structure
- Document the new Feature-Centric architecture in README.md

themes/engine/sddm/nomarchy/metadata.desktop

@@ -0,0 +1,7 @@
+[SddmGreeterTheme]
+Name=Nomarchy
+Description=Minimal terminal-style login theme matching the Limine bootloader aesthetic
+Author=Nomarchy
+Type=sddm-theme
+Interface=Qt5
+Version=1.0