feat: allow specifying a css layer for ionic component styles to go in

### Prerequisites

- [x] I have read the [Contributing Guidelines](https://github.com/ionic-team/ionic-framework/blob/main/docs/CONTRIBUTING.md#creating-an-issue).
- [x] I agree to follow the [Code of Conduct](https://ionicframework.com/code-of-conduct).
- [x] I have searched for [existing issues](https://github.com/ionic-team/ionic-framework/issues) that already include this feature request, without success.

### Describe the Feature Request

Please add ability to specify a css cascade layer for Ionic components (Vue or any framework) to use for styling. Although you can import the core styles into a layer like this:
```css
@import '@ionic/vue/css/core.css' layer(ionic);
```
But the component-specific styles are importing indirectly via the component (e.g., Vue/Vite), so there is no way to currently specify a layer for them.

### Describe the Use Case

Tailwind v4 added native css cascade layers. So if Ionic components style without a layer, then Ionic always overrides private application styles using tailwind. If Ionic were to specify a layer, then it would enable the ability to override the styles.

### Describe Preferred Solution

_No response_

### Describe Alternatives

_No response_

### Related Code

_No response_

### Additional Information

_No response_