build(desktop-backend): 打包后端时注入版本信息并同步 native 资源

- 从 desktop/package.json 读取版本号并生成 PyInstaller version-file
- 打包后复制 native 目录到 resources/backend/native，避免 onefile 临时目录依赖
- 将 pyproject.toml 复制到 backend 资源目录，补齐运行时项目标记
- 更新 .gitignore，忽略 backend/native 与 backend/pyproject.toml 打包产物

.gitignore

@@ -44,6 +44,8 @@ pnpm-lock.yaml
 /desktop/resources/ui/*
 !/desktop/resources/ui/.gitkeep
 /desktop/resources/backend/*.exe
+/desktop/resources/backend/native/*
+/desktop/resources/backend/pyproject.toml
 !/desktop/resources/backend/.gitkeep
 /desktop/resources/icon.ico