New AdjustmentsConfig with brightness, contrast, saturation, sharpen,
grayscale, sepia, crop to aspect ratio, trim whitespace, and canvas
padding. All wired from UI through to executor.
- Saturation uses luminance-based color blending
- Sepia uses standard matrix transformation
- Crop calculates center crop from aspect ratio
- Trim whitespace detects uniform border by corner pixel comparison
- Canvas padding adds white border around image
lashman
f71b55da72