bug: beacon incorrectly changes ethernet domain names when choosing a custom mDNS Hostname

[ES-Alexander]

Bug description

By default the ethernet interface is accessible via blueos.local, blueos-ethernet.local, and companion.local.

After configuring a custom mDNS hostname the defaults get ignored and overwritten, after which it's only possible to access the ethernet interface via blueos.local and <custom>.local, which I believe (for consistency with the defaults) should instead be blueos.local, <custom>-ethernet.local, companion.local, and possibly <custom>.local.

A pretty straightforward implementation would be to replace blueos with <custom> in each of the strings, and then if blueos is not in the list anymore append it.

Steps to reproduce

1. Open a fresh install of BlueOS, or delete the beacon configs from the File Browser and restart the core container
2. Access BlueOS via blueos-ethernet.local or companion.local
3. Edit Vehicle Details in some way (even just changing the Vehicle Name still triggers the hostname overwrite)
4. The page is no longer accessible, and the new hostname cannot be used with the -ethernet suffix

Primary pain point(s)

Intended behaviour doesn't work, and failing to connect to the interface is a critical issue, especially for users who don't know the default interface names that are always available (e.g. blueos-avahi.local).

Additional context

#1001 is another beacon configuration issue, although I don't believe they're related (but it might be worth trying to fix both at the same time).

Prerequisites

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