a shadow is just a silhouette cast on a surface, so it can move much faster than light. An object moving near the speed of light in front of a small light source that casts a shadow on a very large, very distant object could appear to move billions of times faster than light (though you would need an extremely bright light source for the shadow to be noticeable to the naked eye)

there’s really no upper limit, just how far you’re willing to stretch the definition of “shadow” and “movement”