Add image selection refinement functionality with BEN2 integration

- Implemented viewport.py for handling 3D view projections, gestures, and overlay drawing.
- Created refine_image_selection.py to manage the refinement of gesture masks and output image bounds.
- Added selection module with refine_selection.py to process and crop images based on alpha channel visibility.
- Introduced __init__.py for selection module to expose refine_selection function.

src/anyimage/preferences.py

@@ -113,7 +113,7 @@ class AnyImagePreferences(bpy.types.AddonPreferences):
         name="Maximum AI Input Size",
         description=(
             "Maximum source long edge eligible for Upscale and maximum long edge "
-            "used by Depth, Normal and Region refinement"
+            "used by Depth, Normal and Selection refinement"
         ),
         default=DEFAULT_MAX_AI_INPUT_SIZE,
         min=MIN_MAX_AI_INPUT_SIZE,