PVL Color Match

Color transfer between images with optional attention mask. If attention_mask is provided (standard ComfyUI MASK, black/white): - The white region defines the analysis area on BOTH target and reference. - Outside the white region, both images are flattened to the mean color of their own masked region *only for analysis*. - The resulting color correction is then applied to the entire ORIGINAL target image (no masking in the output stage). Based on: https://github.com/hahnec/color-matcher/