Keyboard events (Enter/Escape) are already handled globally in app.rs
subscription and work correctly with Crop mode detection.
Widget-level keyboard events don't work without focus anyway.
Only mouse events (click, drag, double-click) stay in the widget.
B1: Fixed handle positions - now uses relative coordinates correctly
- Handles are drawn at correct positions (relative to bounds)
- Conversion between screen and relative coords
B2: Added Enter and Double-click for Apply
- Enter key applies crop when selection exists
- Escape key cancels crop
- Double-click on selection center applies crop (400ms window)
- CropRegion moved to domain/document/operations/crop.rs (pure model)
- crop_types.rs renamed to crop_model.rs (honest UI model name)
- DragHandle and CropSelection stay in UI layer (where they belong)
- Clean separation: Domain has no UI concerns, UI imports from Domain
