Allow widget rotations

Idea raised in [this forum post](https://discuss.bluerobotics.com/t/rotating-the-stream-video-view-90-degrees/12319), where a user wanted to rotate their camera stream to on its side, and compensate for the rotation in the display software.

Should be constrained to particular widgets (since it gets complicated and probably unhelpful if text is involved), but unsure if it should be enabled via a flag, or if it's just restricted to only video widgets. It's likely sufficient to only support 90 degree rotations, if that's easier to implement than allowing general rotations, but otherwise we could have 45 and/or 30 degree rotations as snap points.

Start with the linked forum post, then trace the widget and video-stream rendering entry points to determine where rotation belongs. Resolve whether rotation is limited to video widgets and which snap angles are supported; done means the chosen behavior is implemented and verified for the applicable widgets.

Written by the indexing model from the issue text.