Add one-click installation script for Headscale clients

- Complete automated script for Tailscale + Headscale registration
- Support for Ubuntu, Debian, CentOS, RHEL, Rocky, Fedora, Arch
- Universal binary fallback for unsupported distros
- Automatic firewall configuration
- Network connectivity verification
- Fix Headscale health check (nc -> headscale version)
- Add comprehensive error handling and colored output

🚀 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

docker-compose.yml

@@ -18,7 +18,7 @@ services:
     networks:
       - headscale-net
     healthcheck:
-      test: ["CMD-SHELL", "nc -z localhost 8080 || exit 1"]
+      test: ["CMD", "/ko-app/headscale", "version"]
       interval: 30s
       timeout: 10s
       retries: 3