[v5] Tree background color in move dialog broken

[distantnative]

The rows shouldn't have a gray background but be just transparent as long as not hovered or selected:

@bastianallgeier As far as I understand, this is the result of trying to control the browser/tree hover state colors working well against a defined background. Do you think there is a way to make this work more flexibly without actually fixing a tree background color, but leaving it transparent?

Or do we need to define special CSS color rules for the move dialog?