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.
Create a new `settings.py` file to define and manage global application paths.
Modify UI components (`split_view_widget.py`, `view_settings_dialog.py`) to use the centralized `ICONS_DIR` path constant instead of hardcoded relative paths for icons. This improves maintainability and makes the application independent of the working directory.
