Set WiFi ssid and password via serial cli

[mikecarper]

Make it not need a build, allowing for a 3rd type to be used from the web flasher

[recrof]

@mikecarper I see you pretty active on the issues department, how about some PRs? :)

[mikecarper]

Point me where this change would go and I'll give it a go

[mrlmuk]

Surely this isn't possible untill the firmware for usb/bt/wifi are combined onto one? I think that's planned for the future.

[MarekWo]

I'm a Heltec V4 user running a companion radio over WiFi/TCP. Currently the only way to keep my SSID/password through a firmware upgrade is a local git stash → git pull → git stash pop → pio run -t upload workflow every release, since the credentials live as -D WIFI_SSID / -D WIFI_PWD build flags in variants/heltec_v4/platformio.ini. Runtime configuration would be a big quality-of-life improvement, especially for users flashing prebuilt binaries from the web flasher.

Worth noting that two open PRs already implement most of this:

• feat: Add companion WiFi CLI #2217 (dz0ny) — persists wifi_ssid / wifi_pwd to NodePrefs + DataStore, exposed via CLI. Linked to this issue.
• feat: wifi companion configuration via cli rescue #2720 (NickDunklee) — smaller CLI-rescue approach (wifi_ssid, wifi_pwd, wifi_commit, wifi_clear).

It would be great if a maintainer could review either of them.