OpenWrt packaging

Packaging sources for the official OpenWrt .ipk release artifacts (issue #284).

build-ipk.sh — assembles opkg-format .ipk packages from a prebuilt static musl binary, without the OpenWrt SDK. Run with no arguments for usage.
meow/files/ — procd init scripts (meow.init, meow-arp.init), /etc/config/meow UCI settings, the default /etc/meow/config.yaml, gateway.sh (transparent-proxy nftables rules for gateway / side-router mode: kernel TPROXY or REDIRECT, plus the per-client MAC bypass set managed from the LuCI Clients tab), and arp-hijack.sh (opt-in, off-by-default ARP-based client steering, an advanced section of the Clients tab — ARP spoofing, for devices you administer only).
luci-app-meow/ — LuCI app: root/ overlays / on the device, htdocs/ maps to /www. Overview, config editor, clients, settings and log views talk to the meow REST API and UCI; the Panel tab embeds the built-in web UI served at /ui instead of reimplementing a dashboard.
docker/side-router.sh — runs OpenWrt in a Docker container on the LAN (macvlan, bridge mode) configured as a side router with meow installed.

Release wiring lives in .github/workflows/release.yml (ipk matrix), the Docker end-to-end test in tests/test_openwrt_docker.sh, and user-facing documentation in docs/openwrt.md.