- Add --set KEY=VALUE and env vars DNSMASQ_WEBUI_* to configure app at install
- Write env file for systemd (system: /etc/default/dnsmasq-webui; user: install-dir/dnsmasq-webui.env)
- Default ASPNETCORE_URLS=http://0.0.0.0:8080 so service listens on 8080
- Preserve existing env file on update (only overwrite when new config or first install)
- README: configure-at-install section, --set in options table, update preserves env note
- README: use master branch in raw GitHub URL (repo default branch)
- install.sh: trim repo and asset URLs (fix malformed URL when script has CRLF or trailing whitespace)