feat: add WebSocket router for real-time broadcast updates

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/routers/ws.py

@@ -0,0 +1,30 @@
+import asyncio
+import json
+from fastapi import APIRouter, WebSocket, WebSocketDisconnect
+
+router = APIRouter()
+
+connected_clients: list[WebSocket] = []
+
+
+@router.websocket("/ws")
+async def websocket_endpoint(ws: WebSocket):
+    await ws.accept()
+    connected_clients.append(ws)
+    try:
+        while True:
+            await ws.receive_text()
+    except WebSocketDisconnect:
+        connected_clients.remove(ws)
+
+
+async def broadcast(event_type: str, data: dict):
+    message = json.dumps({"type": event_type, "data": data})
+    disconnected = []
+    for ws in connected_clients:
+        try:
+            await ws.send_text(message)
+        except Exception:
+            disconnected.append(ws)
+    for ws in disconnected:
+        connected_clients.remove(ws)