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/static/js/features/graph-editor.ts

@@ -1528,7 +1528,7 @@ function _onTestNode(node: any) {
         value_source: () => _w.testValueSource?.(node.id),
         color_strip_source: () => _w.testColorStrip?.(node.id),
         cspt: () => _w.testCSPT?.(node.id),
-        output_target: () => _w.testKCTarget?.(node.id),
+        output_target: undefined,
     };
     fnMap[node.kind]?.();
 }