Refactor image processing and cutout functionalities

- Updated the naming convention for upscaled images to include underscores and file extensions.
- Renamed properties related to cutout pixel size to point spacing for clarity.
- Adjusted alpha region calculations to use a half-alpha threshold for better accuracy.
- Enhanced the handling of foreground mesh masks to consider half-alpha values.
- Introduced new functions for unbounded selections and cutout images, ensuring proper handling of source and selection images.
- Improved test coverage for cutout functionalities, including bounds mapping and alpha preservation.
- Updated tests to reflect changes in naming conventions and functionality adjustments.

docs/server.md

@@ -71,7 +71,7 @@ Image Box 与 Lasso 的 `Refine Selection` 使用 `refine-image-mask` Job。它
 - BEN2 Base
 - Real-ESRGAN General WDN x4v3、SAFMN Real x4、Real-ESRGAN x4plus
 
-Upscale 使用上述三档 4× RGB 模型。正式 `upscale-image` Job 把结果写成 `upscale.0001.png` 起的序列并回写为 `.upscale` Image 数据块；对应 Debug Job 保留模型直通输出，便于横向比较。
+Upscale 使用上述三档 4× RGB 模型。正式 `upscale-image` Job 把结果写成 `upscale.0001.png` 起的序列并回写为 `_upscale.png` Image 数据块；对应 Debug Job 保留模型直通输出，便于横向比较。
 
 首次安装会下载 MoGe-2 ViT-S Normal、BEN2 Base 与默认的 Real-ESRGAN General WDN x4v3。SAFMN Real x4 和 Real-ESRGAN x4plus 可在扩展偏好设置按需下载。模型保存在 `models/`，可由多个 Blender 版本共享。Server 会复用连续任务所需的同一 Session；切换模型族时释放旧 Session，推理资源异常时立即卸载当前高清 Session。