feat: Ion-datetime wheel focused column to be styled with CSS

### 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

- Have a way to style the focused column of an ion-datetime wheel (`preferWheel="true"`).

### Describe the Use Case

- When toggling the different sections of the datetime wheel with the keyboard, we're unable to style the focused element (wheel column), and there is currently no documentation or guide on how to do this


### Describe Preferred Solution

_No response_

### Describe Alternatives

_No response_

### Related Code

_No response_

### Additional Information

_No response_

Start by reviewing the closed, merged pull request #30934 linked to this issue and the ion-datetime wheel behavior it addressed. Confirm whether the focused column can be styled through the existing component surface; done means keyboard-focused wheel columns have a documented, verifiable styling path.

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