System theme detection for Dioxus Desktop (Linux)

## Feature Request

Because of https://github.com/tauri-apps/tauri/issues/9427, Dioxus Desktop on Linux doesn't detect the system (dark) theme. From the last meeting I've understood that it is natively supported for other OSes, but Linux is currently not one of them.

## Implement Suggestion

It is supposed to be fixable via https://github.com/wyhaya/tauri-plugin-theme, but AFAIK Dioxus doesn't support adding Tauri plugins at the moment (https://github.com/DioxusLabs/dioxus/issues/3699).

Start by reviewing issue #3699 and the linked tauri-plugin-theme project to determine whether Dioxus Desktop can support the required plugin path. Confirm how Linux system theme detection should integrate with the desktop target; done means Linux applications detect the system dark theme consistently.

Written by the indexing model from the issue text.