Add new functionality for image rectification and depth metadata handling

- Implemented a preview tool for rectifying images with interactive aspect controls in `preview.py`.
- Added tests for depth metadata loading to ensure consistent schema usage in `test_depth_metadata.py`.
- Developed comprehensive tests for cutout calibration processes in `test_cutout_calibration.py`, including stability checks and depth calibration.
- Created tests for frame compositing operations in `test_frame_compositing.py`, ensuring correct handling of depth and transparency.
- Introduced material slot inheritance functionality in `material_slots.py` to manage geometry material assignments.
- Built shared shader nodes for material processing in `shader.py`, including roughness and bump mapping setups.

.env.example

@@ -0,0 +1,3 @@
+# 复制为 .env，并填写本机 Blender 可执行文件路径。
+# Windows 路径可使用正斜杠。
+BLENDER_BIN="C:/Program Files/Blender Foundation/Blender 4.5/blender.exe"