[Effects] Mandelbrot Set should be centered vertically/horizontally

**Description**
The way we're calculating it now, it gets offset and this can occlude part of the results. Of course we support rotation, so this means we should align the center of rotation as well.

**Additional Info**

<img width="1231" height="797" alt="Image" src="https://github.com/user-attachments/assets/1b87446b-36c6-4c8e-9ebf-758db71ee456" />

**Version**
3.1.2
