fix: backend TS errors — agent role type, WebSocket SocketStream, jwt.sign cast

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

backend/src/types.ts

@@ -2,7 +2,7 @@ export interface JwtPayload {
   sub: string         // user.id (UUID)
   email: string
   name: string
-  role: 'hotel_admin' | 'manager' | 'housekeeper' | 'super_admin' | 'receptionist' | 'accountant' | 'security' | 'technician'
+  role: 'hotel_admin' | 'manager' | 'housekeeper' | 'super_admin' | 'receptionist' | 'accountant' | 'security' | 'technician' | 'agent'
   hotelId: string | null
   hotelSlug: string | null
 }