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-or-focus-webapp

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+# Launch or focus on a given web app identified by the window-pattern.
+# Use by some default bindings, like the one for WhatsApp, to ensure there is only one instance of the application open.
+
+if (($# == 0)); then
+  echo "Usage: nomarchy-launch-or-focus-webapp [window-pattern] [url-and-flags...]"
+  exit 1
+fi
+
+WINDOW_PATTERN="$1"
+shift
+LAUNCH_COMMAND="nomarchy-launch-webapp $@"
+
+exec nomarchy-launch-or-focus "$WINDOW_PATTERN" "$LAUNCH_COMMAND"