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/scripts/battery-monitor.nix

@@ -0,0 +1,34 @@
+{ pkgs, ... }:
+
+{
+  systemd.user.services.nomarchy-battery-monitor = {
+    Unit = {
+      Description = "Nomarchy Battery Monitor Check";
+      After = [ "graphical-session.target" ];
+    };
+
+    Service = {
+      Type = "oneshot";
+      # The script is packaged in nomarchy-scripts which is in the home profile
+      ExecStart = "nomarchy-battery-monitor";
+      Environment = [ "DISPLAY=:0" ];
+      LogLevelMax = "warning";
+    };
+  };
+
+  systemd.user.timers.nomarchy-battery-monitor = {
+    Unit = {
+      Description = "Nomarchy Battery Monitor Timer";
+    };
+
+    Timer = {
+      OnBootSec = "1min";
+      OnUnitActiveSec = "30sec";
+      AccuracySec = "10sec";
+    };
+
+    Install = {
+      WantedBy = [ "timers.target" ];
+    };
+  };
+}