feat(streaming): introduce WebSocket Streaming API bridging event bus

ApiServer: add AsyncWebSocket at /ws; accept JSON {event, payload} (string or object) and dispatch via ctx.fire; mirror all local events to clients using NodeContext::onAny.\nNodeContext: add onAny subscriber API.\nNeoPatternService: add api/neopattern/color event to set solid color.\nCluster: centralize cluster/broadcast sending in core; services delegate.\nAPI: add generic /api/node/event and /api/cluster/event endpoints in respective services.\nTests: add ws-color-client, ws-cluster-broadcast-color, http-cluster-broadcast-color.\nDocs: add StreamingAPI.md; update README and test/README.\nFixes: robust WS JSON parsing on ESP8266 and payload handling.

test/ws-cluster-broadcast-color.js

@@ -0,0 +1,46 @@
+// WebSocket client to broadcast neopattern color changes across the cluster
+// Usage: node ws-cluster-broadcast-color.js ws://<device-ip>/ws
+
+const WebSocket = require('ws');
+
+const url = process.argv[2] || 'ws://127.0.0.1/ws';
+const ws = new WebSocket(url);
+
+const colors = ['#FF0000', '#00FF00', '#0000FF', '#FFFF00', '#FF00FF', '#00FFFF'];
+let idx = 0;
+
+ws.on('open', () => {
+  console.log('Connected to', url);
+  // Broadcast color change every 5 seconds via cluster/broadcast
+  setInterval(() => {
+    const color = colors[idx % colors.length];
+    idx++;
+    const payload = { color, brightness: 128 };
+    const envelope = {
+      event: 'api/neopattern/color',
+      data: payload // server will serialize object payloads
+    };
+    const msg = { event: 'cluster/broadcast', payload: envelope };
+    ws.send(JSON.stringify(msg));
+    console.log('Broadcasted color event', payload);
+  }, 5000);
+});
+
+ws.on('message', (data) => {
+  try {
+    const msg = JSON.parse(data.toString());
+    console.log('Received:', msg);
+  } catch (e) {
+    console.log('Received raw:', data.toString());
+  }
+});
+
+ws.on('error', (err) => {
+  console.error('WebSocket error:', err.message);
+});
+
+ws.on('close', () => {
+  console.log('WebSocket closed');
+});
+
+