Per-model theme / background image selection (color radios)

[mnorden81]

Feature request

Currently the theme (colors and background image) is a global radio setting
(SYS → Themes → Set Active). The background image is part of the theme, so it
cannot differ between models. Only the model image can be set per model.

Use case

With many models (planes, boats, cars) it would be helpful to see at a glance
which model is loaded, e.g. via a model-specific background image or color
scheme. Today the only workaround is a model image widget on the main view,
which does not fill the screen or sit behind other widgets.

Proposal

One of the following (in order of preference):

1. A "Theme" field in Model Setup that overrides the active radio theme while
   the model is loaded (default: "Radio default").
2. Alternatively, only a per-model background image override, keeping the
   global colors.

Radio / version

RadioMaster TX16S, EdgeTX nightly build of 2026-10-17 (480x272 color LCD)

I searched existing issues and discussions and found no matching request.
Happy to help with testing.

[pfeerick]

#1681 🙈 🤣

[mnorden81]

Thx