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

features/apps/scripts/nomarchy-launch-webapp

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+# Launch the passed in URL as a web app in the default browser (or chromium if the default doesn't support --app).
+
+browser=$(xdg-settings get default-web-browser)
+
+case $browser in
+google-chrome* | brave-browser* | microsoft-edge* | opera* | vivaldi* | helium*) ;;
+*) browser="chromium.desktop" ;;
+esac
+
+exec setsid uwsm-app -- $(sed -n 's/^Exec=\([^ ]*\).*/\1/p' {~/.local,~/.nix-profile,/usr}/share/applications/$browser 2>/dev/null | head -1) --app="$1" "${@:2}"