System Tray improvements

New Feature

What does this MR do?

This MR adds several improvements to the system tray functionality of the desktop app.

It allows a show/hide toggle from the system tray menu.

It add a new UI setting: start in Tray, which, at desktop app startup, will hide the main window.

Related issues

Closes #230 (closed)

Checklist

• Application works as expected when running from source
• There are dependency changes
• Liquidctl device mock tests are successful (if applicable)
• Any needed documentation changes have been made
• This MR is ready to be merged