Unfortunately, Godot only supports using static images as a panorama. Using a video would mean the radiance map would need to be updated (at least) 24 times a second, which is too fast for the current radiance map implementation. This might be doable in Godot 4.0, but keep in mind decoding high-resolution video on the CPU has a significant cost.
I suggest making the planet use a MeshInstance with a SphereMesh and rotate it using an AnimationPlayer node. It won't appear in the reflections this way, but at least it'll be able to move :)