bug: WIFI_STATUS_FETCH_FAIL spam with no wlan

### 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

- [x] I have checked to make sure that a similar request has not already been filed or fixed.