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

themes/engine/scripts/nomarchy-theme-remove

@@ -0,0 +1,35 @@
+#!/bin/bash
+
+# nomarchy-theme-remove: Remove a theme from Nomarchy by name
+# Usage: nomarchy-theme-remove <theme-name>
+
+if [[ -z $1 ]]; then
+  mapfile -t extra_themes < <(find ~/.config/nomarchy/themes -mindepth 1 -maxdepth 1 -type d ! -xtype l -printf '%f\n')
+
+  if (( ${#extra_themes[@]} > 0 )); then
+    THEME_NAME=$(printf '%s\n' "${extra_themes[@]}" | sort | gum choose --header="Remove extra theme")
+  else
+    echo "No extra themes installed."
+    exit 1
+  fi
+else
+  THEME_NAME="$1"
+fi
+
+THEMES_DIR="$HOME/.config/nomarchy/themes"
+CURRENT_DIR="$HOME/.config/nomarchy/current"
+THEME_PATH="$THEMES_DIR/$THEME_NAME"
+
+# Ensure a theme was set
+if [[ -z $THEME_NAME ]]; then
+  exit 1
+fi
+
+# Check if theme exists before attempting removal
+if [[ ! -d $THEME_PATH ]]; then
+  echo "Error: Theme '$THEME_NAME' not found."
+  exit 1
+fi
+
+# Now remove the theme directory for THEME_NAME
+rm -rf "$THEME_PATH"