Module mode 

Application mode: Development vs Production.

Controls framework behavior such as startup banner verbosity and built-in request logging.

环境识别遵循 ASP.NET Core 约定：

1. 环境变量 APP_ENV（不区分大小写）显式指定，取值 Production/Prod 或 Development/Dev；
2. 未设置时默认 Development。

框架据此自动加载 appsettings.{Environment}.json overlay。

Enums

AppMode

Controls how the framework behaves at startup and at runtime.