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-setup-fido2

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+
+# Configure FIDO2 support declaratively for Nomarchy NixOS.
+
+STATE_FILE="/etc/nixos/state.json"
+
+if [[ "--remove" == $1 ]]; then
+    sudo jq '.features.fido2 = false' "$STATE_FILE" > /tmp/state.json && sudo mv /tmp/state.json "$STATE_FILE"
+    echo "FIDO2 support disabled. Applying changes..."
+    sudo sys-update
+    exit 0
+fi
+
+sudo jq '.features.fido2 = true' "$STATE_FILE" > /tmp/state.json && sudo mv /tmp/state.json "$STATE_FILE"
+echo "FIDO2 support enabled. Applying changes..."
+sudo sys-update
+
+# Enrollment is still an imperative action
+if command -v pamu2fcfg &> /dev/null; then
+    echo "Let's register your FIDO2 key now."
+    mkdir -p ~/.config/Yubico
+    pamu2fcfg > ~/.config/Yubico/u2f_keys
+    echo "FIDO2 key registered."
+else
+    echo "pamu2fcfg not found. It will be available after the next reboot or sys-update."
+fi