feat(systray): add volume limiter toggle to tray menu

[CaWu009]

What

Adds a volume limiter toggle to the system tray context menu,
positioned below "Open Arctis Manager".

The toggle is only shown when the connected device supports
volume limiter (Nova 5, Nova 7, Nova Pro).

Why

Previously, toggling volume limiter required opening the full
main window. This makes it accessible with a single right-click
on the tray icon.

Changes

• systray_app.py: subscribe to settings, add checkable
  QAction for volume limiter
• dbus_wrapper.py: subscribe to SettingsChanged D-Bus signal
  so all clients stay in sync when settings change from any source

[elegos]

Hello @CaWu009 ,

I'm sorry, but I can't accept this merge request at this stage: the setting is not supported on all devices, and would lead to confusion for people not having it.

I can propose you a couple of alternative solutions:

1. Make a new section in the main window "Systray toggles" where you can enable or disable all the toggable options, per device. This would let the user select whatever settings he/she wants to have as a shortcut in the system tray app
2. Add support for keyboard shortcuts (again: toggable options only) with a notification about the change. The shortcut management should be done again based on the list of available options for the current device.

In any case both the solutions would need a management whenever the device is turned on (refresh of the toggable options / shortcuts) and off (removal of toggable options / shortcuts)

[CaWu009]

Thanks for the detailed feedback — makes sense, hard-coding a single setting wasn’t the right approach.

I’ve reworked the PR around Option 1. The volume-limiter special case is gone now. Instead, there’s a new “Systray toggles” section in the main window where the user can pick which toggle settings should show up in the tray menu.

The list is built from settings_config for the connected device, so it’s not tied to any specific setting. If a device doesn’t expose any toggle settings, the section just stays empty.

A few other changes included:

• systray toggle selection is saved per device, in the device settings file
• old flat-format settings are still read for compatibility
• the tray menu now only shows pinned toggles for the current device
• connect/disconnect now emits SettingsChanged, so the panel and tray refresh properly when a device is connected or removed
• added SetSystrayToggle as a D-Bus method for this UI preference
• documented it in docs/dbus.md
• added tests for settings persistence and the D-Bus service

I left the keyboard-shortcuts part out for now to keep this PR focused. That can be a separate change later if you still want it.

One thing I’m not fully sure about is the layout: I put this in its own side-panel section for now, but I can also move it into the existing Device panel, for example as a “show in tray” checkbox next to each toggle.