feat(m2): live video to stock Moonlight — ENet control + video data plane

A stock Moonlight client now decodes H.265 from the lumen host end-to-end
(verified at 5120×1440@120 on RTX 5070 Ti):
- control.rs: ENet control host on UDP 47999 (rusty_enet). Moonlight starts the
  control stream before video (STAGE_CONTROL_STREAM_START precedes _VIDEO_), so it
  must be up first — this was the blocker behind the earlier "error 35".
- stream.rs: video data plane — on RTSP PLAY, learn the client endpoint from its
  ping, NVENC-encode at the negotiated mode, packetize (GameStream RTP/NV/FEC),
  send over UDP 47998; stops when the client disconnects.
- rtsp.rs: ANNOUNCE → StreamConfig (resolution/fps/packetSize/bitrate/codec), PLAY
  starts the stream, TEARDOWN stops it; PairStatus=1 over the mutual-TLS port.

P1.3 uses a synthetic test pattern + data-shards-only FEC (clean-LAN). Next: real
portal desktop capture, input injection (decode control → uinput), nanors-exact FEC,
encryption, audio.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/lumen-host/Cargo.toml

@@ -26,6 +26,7 @@ x509-parser = "0.16"
 axum-server = { version = "0.7", features = ["tls-rustls"] }
 rustls = "0.23"
 rustls-pemfile = "2"
+rusty_enet = "0.4"
 
 [target.'cfg(target_os = "linux")'.dependencies]
 # `screencast` gates the ScreenCast portal module; `tokio` is the default runtime.