bug: WIFI_STATUS_FETCH_FAIL spam with no wlan #4210

Bug description

WifiUpdater polls /wifi/status every 5s and pushError('WIFI_STATUS_FETCH_FAIL') when wlan0 is missing. The wifi service raises FetchError instead of returning { available: false }.

Related #4204

Steps to reproduce

1. Run BlueOS on a board with no wlan0 or wifi disabled
2. Open the frontend

Primary pain point(s)

Notification tray and logs fill with WIFI_STATUS_FETCH_FAIL / WIFI_SAVED_FETCH_FAIL

Additional context

https://discuss.bluerobotics.com/t/suppress-error-messages-from/21862

Prerequisites

• I have checked to make sure that a similar request has not already been filed or fixed.