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

core/system/scripts/nomarchy-battery-present

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+# Returns true if a battery is present on the system.
+# Used by the battery monitor and other battery-related checks.
+
+for bat in /sys/class/power_supply/BAT*; do
+  [[ -r $bat/present ]] &&
+  [[ $(cat $bat/present) == "1" ]] &&
+  [[ $(cat $bat/type) == "Battery" ]] &&
+  exit 0
+done
+
+exit 1