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/utils/nomarchy-snapshot

@@ -0,0 +1,34 @@
+#!/bin/bash
+
+set -e
+
+COMMAND="$1"
+NOMARCHY_PATH=${NOMARCHY_PATH:-$HOME/.local/share/nomarchy}
+
+if [[ -z $COMMAND ]]; then
+  echo "Usage: nomarchy-snapshot <create|restore>" >&2
+  exit 1
+fi
+
+if ! command -v snapper &>/dev/null; then
+  exit 127 # nomarchy-update can use this to just ignore if snapper is not available
+fi
+
+case "$COMMAND" in
+create)
+  DESC="$(nomarchy-version)"
+
+  echo -e "\e[32mCreate system snapshot\e[0m"
+
+  # Get existing snapper config names from CSV output
+  mapfile -t CONFIGS < <(sudo snapper --csvout list-configs | awk -F, 'NR>1 {print $1}')
+
+  for config in "${CONFIGS[@]}"; do
+    sudo snapper -c "$config" create -c number -d "$DESC"
+  done
+  echo
+  ;;
+restore)
+  sudo limine-snapper-restore
+  ;;
+esac