fix(tray): Linux tray icon duplicates and dead menus on minimize-to-tray toggle (#5086)

On Linux, `Tray.destroy()` does not remove the icon from StatusNotifierItem
hosts (waybar, KDE Plasma), so toggling "Minimize to tray" off and on stacked a
dead icon every time. Keep the single Tray instance for the app's lifetime
instead; the window close handler reads `getTrayConfig()` live, so a tray icon
that outlives a disabled setting is inert.

The icon cannot be removed from a running process, so `setTrayConfig` reports
when a restart is needed and the renderer offers one via a new `app.relaunch`
IPC. That relaunch runs from `$APPIMAGE` where set (AppImage's `execPath` points
into a mount that is gone by then), drops `--start-in-tray` so it never comes
back hidden, and uses `app.quit()` so `before-quit` still persists the window
bounds and flushes cookies.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>