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/scripts/nomarchy-font-list

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Returns a list of all the monospace fonts available on the system that can be set using nomarchy-font-set.
+
+fc-list :spacing=100 -f "%{family[0]}\n" | grep -v -i -E 'emoji|signwriting|nomarchy' | sort -u