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-pkg-add

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+
+PKG_NAME="$1"
+
+if [ -z "$PKG_NAME" ]; then
+    echo "Usage: nomarchy-pkg-add <package-name>"
+    exit 1
+fi
+
+STATE_FILE="$HOME/.config/home-manager/user-packages.json"
+mkdir -p "$(dirname "$STATE_FILE")"
+
+if [ ! -f "$STATE_FILE" ]; then
+    echo "[]" > "$STATE_FILE"
+fi
+
+if jq -e --arg pkg "$PKG_NAME" '. | index($pkg)' "$STATE_FILE" >/dev/null; then
+    echo "Package $PKG_NAME is already in your user-packages.json"
+    exit 0
+fi
+
+# Append package to the JSON array safely
+jq --arg pkg "$PKG_NAME" '. + [$pkg]' "$STATE_FILE" > "${STATE_FILE}.tmp" && mv "${STATE_FILE}.tmp" "$STATE_FILE"
+
+echo "Package $PKG_NAME added declaratively to $STATE_FILE."
+echo "Applying changes with env-update..."
+env-update