Function AuthShell 

pub(crate) fn AuthShell(props: AuthShellProps) -> impl IntoView

登录与注册共用的外壳：文字标、居中面板、返回首页。

Required Props

• title: [&'static str]
• children: [Children]
• footer: impl Into<ViewFn>

Optional Props

• subtitle: [&'static str]