feat: HA light target live color preview — per-entity swatches via WebSocket

- Cache per-entity colors in HALightTargetProcessor._update_lights()
- Broadcast colors_update to WS clients at target's update_rate
- WS endpoint: /api/v1/output-targets/{target_id}/ha-light/ws
- Frontend: connect WS when target runs, update swatch colors live
- Card shows colored boxes per mapped entity with entity name labels

server/src/wled_controller/main.py

@@ -233,7 +233,6 @@ async def lifespan(app: FastAPI):
 
     logger.info(f"Registered {len(devices)} devices for health monitoring")
 
-    # Migrate KC targets → key_colors CSS sources
     # Register output targets in processor manager
     targets = output_target_store.get_all_targets()
     registered_targets = 0