Refactor the image rotation mechanism in the `SplitView` widget to prevent image quality degradation.
- The original reference pixmap is now stored in `self.original_ref_pixmap`.
- Rotations are always applied to the original, unmodified pixmap, using a cumulative rotation angle.
- This avoids sequential transformations that caused gradual quality loss.
- Also fixes indentation issues caused by previous automated replacements.
bartool
03ab345e17