[Teaser] Saving without Alt Text with Image

## Bug Report

**Current Behavior**
In the Teaser component, if you have an image saved with alt text filled out, it is possible to delete the alt text and re-save an empty field without error. The field is marked as required but is not behaving as required.

**Expected behavior/code**
Alt text should be required and behave as required when an Image is present whether it already existed or is newly uploaded.

**Environment**
- AEM SDK Version - 2025.5.21005.20250522T173058Z-250400
- Core Components version 2.29.0
- JRE version 11.0.27 2025-04-15 LTS

**Possible Solution**
The existing toggles for requiring the alt text don't update the marking for being required. Additionally, the required state doesn't seem to be available on load when an image is already present.

**Additional context / Screenshots**

https://github.com/user-attachments/assets/ea220da0-470e-4884-b62f-0af9c0518666

Start with the Teaser component's image and alt-text field, reproducing the case where existing alt text is deleted and saved. Inspect how the required marking and validation respond when an image is already present or newly uploaded; done means an empty alt-text field cannot be saved in either case.

Written by the indexing model from the issue text.