feat: implement modular foundation and core system services

- Update flake.nix with 25.11 release and core inputs
- Add dedicated modules for audio (Pipewire), bluetooth, and networking
- Update GEMINI.md with the new Modular Merging Architecture blueprint
- Configure graphical installer ISO and test VM outputs

bin/nomarchy-install-tailscale

@@ -1,10 +1,25 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
-# Install the Tailscale mesh VPN service and a web app for the Tailscale Admin Console.
+# Configure Tailscale declaratively for NixOS
 
-curl -fsSL https://tailscale.com/install.sh | sh
+FEATURE_FILE="/etc/nixos/nomarchy-features/tailscale.nix"
 
-echo -e "\nStarting Tailscale..."
-sudo tailscale up --accept-routes
+if [ -f "$FEATURE_FILE" ]; then
+    echo "Tailscale is already configured in $FEATURE_FILE"
+    exit 0
+fi
+
+sudo mkdir -p "/etc/nixos/nomarchy-features"
+cat <<EOF | sudo tee "$FEATURE_FILE" > /dev/null
+{ config, pkgs, ... }:
+{
+  services.tailscale.enable = true;
+}
+EOF
+
+echo "Created $FEATURE_FILE."
+echo "IMPORTANT: To finish enabling Tailscale, add './nomarchy-features/tailscale.nix' to your imports list in /etc/nixos/system.nix or /etc/nixos/flake.nix,"
+echo "then run 'sys-update'."
+echo "After sys-update completes, you can log in by running 'sudo tailscale up'."
 
 nomarchy-webapp-install "Tailscale" "https://login.tailscale.com/admin/machines" https://cdn.jsdelivr.net/gh/homarr-labs/dashboard-icons/png/tailscale-light.png