Initial scaffold: FastAPI backend + Vue 3 frontend + Docker setup

Backend: config/db/security/logging core, SQLAlchemy models (Server,
Credential, UpdateJob, UpdateLog, AuditLog, User), services (winrm, ssh,
cau, audit, job_runner), REST API (auth, servers, updates, audit),
Socket.io WebSocket layer.
Frontend: Vue 3 + TS + Pinia + Tailwind, Views (Dashboard, Servers,
Updates, Audit, Login), axios + socket.io-client, nginx prod config.

backend/app/websocket/__init__.py

@@ -0,0 +1,6 @@
+"""WebSocket layer: Socket.io server, connection manager, event handlers."""
+
+from app.websocket.handlers import sio
+from app.websocket.manager import WSManager, ws_manager
+
+__all__ = ["WSManager", "sio", "ws_manager"]