## is_healthy() Check whether the server is reachable and the stored credentials are valid. Usage ``` python is_healthy(timeout_config=None) ``` Issues an authenticated GET to the Listmonk health endpoint using the cached username and password. This call is defensive: any failure--the URL base not being set, not being logged in, a network error, a non-2xx response, or an unparseable body--is caught and reported as False, so it never raises. ## Parameters `timeout_config: Optional[httpx2.Timeout] = None` Optional per-request timeout; defaults to 10 seconds. ## Returns `bool` True if the server responded healthy with valid credentials, False otherwise.