[Devcontainers frontend plugin] Make the component hidden if no annotation is present

If the annotation is not present, make the `DevcontainersProvider` component hidden.

This should be working in `packages/app/src/components/catalog/EntityPage.tsx`:

```









```

The `isDevContainersAvailavble` function should check if the correct annotations are in place like (pseudocode):
```
export const isDevContainersAvailable = (entity: Entity) =>
Boolean(entity.metadata.annotations?.[DEVCONTAINERS_ANNOTATION]);
```

This way the item can be hidden and the page can be cleaner.

从 packages/app/src/components/catalog/EntityPage.tsx 开始，检查 DevcontainersProvider EntitySwitch case，以及现有的 DEVCONTAINERS_ANNOTATION 和 isDevContainersAvailable 引用。当缺少 annotation 时组件被隐藏，并且存在正确的 annotation 时组件仍然可见，即表示完成。

由索引模型根据 Issue 内容生成。