Add WLED's native realtime UDP protocol (port 21324) as a third output mode for
LED targets, alongside DDP and HTTP. For the device LedGrab drives most, this
brings three user-visible wins DDP lacks:
- Auto-revert: every packet carries a timeout byte, so if the stream stops
(host hiccup/sleep/crash) WLED returns to its preset instead of freezing on
the last frame.
- Correct RGBW whites: the DRGBW variant carries an explicit white channel.
- Lighter on weak Wi-Fi: raw RGB with a 2-byte header.
New WledRealtimeClient auto-selects DRGB (<=490), DRGBW (<=367), or chunked
DNRGB (>490). WLED applies its own per-bus colour order in realtime mode, so we
send plain RGB and the user's colour-order config just works. Protocol 'udp' is
threaded through WLEDConfig/provider/processor and the schema pattern; the
target editor gains a protocol option + badge + i18n (en/ru/zh).
8 unit tests for the packet builder; full suite green (1919 passed).
