Update: Adapt tray icon to theme changes

[HO-COOH]

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This PR will utilize Community ToolKit's ThemeListener and update the tray icon to the correct light/dark mode in time. Unlike currently it only updates when there is a package update check, causing this

But the current ThemeListener does not work under WinUI3, and I have submitted another PR to them to get that fixed. I will mark this WIP with draft for now, and will switch the status to be ready once that PR gets merged.