Fix macOS shadow on first render

[maxichrome]

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For some reason, calling NSWindow::invalidateShadow doesn't recompute the native shadow on macOS — you have to resize the window for the native shadow to display. :|

[maxichrome]

I attempted to debug this by adding a 1-second delay after app render, then calling a custom fix_shadow function:

https://github.com/spacedriveapp/spacedrive/blob/c73c175cf0a5e81f5d3f514365109f2af45f492a/apps/desktop/src-tauri/src/main.rs#L48-L50

Which subsequently runs NSWindow::invalidateShadow():

https://github.com/spacedriveapp/spacedrive/blob/db312269abd99f1d54ab010bda1c3a002853feb3/apps/desktop/src-tauri/src/window.rs#L97-L101

But still no luck until the window is resized