fix: rename src/websocket to src/ws_manager to avoid websocket-client clash

selenium depends on websocket-client which installs a top-level
`websocket` package that shadows our src/websocket/ module on CI.
Renaming to ws_manager eliminates the conflict entirely — no more
sys.path hacks needed in conftest or Selenium tests.

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

src/dashboard/routes/swarm_ws.py

@@ -9,7 +9,7 @@ import logging
 
 from fastapi import APIRouter, WebSocket, WebSocketDisconnect
 
-from websocket.handler import ws_manager
+from ws_manager.handler import ws_manager
 
 logger = logging.getLogger(__name__)