feat(devices): LIFX LAN target type

Adds support for LIFX smart bulbs and lightstrips that speak the LIFX
binary UDP protocol on port 56700, with broadcast LAN discovery via the
standard GetService/StateService probe.

Backend:
- LIFXClient is a single-pixel UDP adapter: averages the strip to one
  RGB triple, converts to LIFX HSBK (16-bit hue/saturation/brightness +
  kelvin), and pushes a tagged SetColor packet so all bulbs on the
  subnet act on it. Brightness folds into the HSBK brightness channel.
- Hand-rolled packet builder: 36-byte LIFX header (frame +
  frame-address + protocol-header) + variable-length payload. Source
  ID 'LGGR' identifies LedGrab in protocol logs.
- supports_fast_send=True with a synchronous send_pixels_fast hot path
  -- UDP costs nothing, so the default rate gate is 50 ms (~20 Hz) to
  match LIFX's documented <=20 cmd/sec recommendation.
- Broadcast discovery sends GetService and parses StateService replies
  back into IP + MAC + service-port triples. Broadcast failures yield
  [] rather than raising.
- Health check sends GetService and waits 1.5s for any reply on a
  one-shot UDP socket.
- LIFXConfig joins the typed config union; Device storage gains a
  lifx_min_interval_ms field; full to_dict/from_dict/to_config wiring.
- 47 unit tests cover URL parsing, RGB->HSBK conversion (red/green/
  blue/white/black/clamping), packet construction (size, msg type,
  tagged flag, target MAC, sequence byte), SetColor and SetPower
  payload layouts, StateService reply parsing (including rejection
  of wrong msg types and runt payloads), strip averaging, rate
  limiting, fast-send hot path, provider validate/discover/health,
  and Device.to_config round-trip.

Frontend:
- 'lifx' in DEVICE_TYPE_KEYS (next to 'wiz'), lightbulb icon
  (deliberate smart-bulb family grouping with Hue + Yeelight + WiZ).
- isLifxDevice predicate + per-type field show/hide in create and
  settings modals.
- Rate-limit number input (default 50 ms) in both modals with hint
  text referencing LIFX's documented <=20 cmd/sec ceiling.
- Locale strings in en/ru/zh.

LIFX bulbs are reachable from the existing "Scan network" button -- no
new discovery UI affordance was needed. No brightness_control capability
exposed; LIFX brightness is folded into the HSBK on the wire.

TODO.md

@@ -723,9 +723,12 @@ After phase 1 the codebase will have 3 fresh examples of "ping the LAN, listen f
 
 ### Phase 4 — Major consumer brands
 
+- [x] **LIFX LAN** — UDP binary protocol on port 56700; RGB→HSBK 16-bit
+      conversion; broadcast discovery via GetService/StateService probe;
+      47 unit tests. Single-pixel adapter shape, identical to WiZ
+      structurally. Frontend wired via subagent.
 - [ ] Govee LAN API (2023+)
 - [ ] Twinkly
-- [ ] LIFX LAN
 - [ ] Nanoleaf OpenAPI
 - [ ] Mi-Light / MiBoxer UDP gateway