[BUG] [Android] Popup V2 - Accessibility: screen reader focus issue

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Did you read the "Reporting a bug" section on Contributing file?

- [x] I have read the "Reporting a bug" section on Contributing file: https://github.com/CommunityToolkit/Maui/blob/main/CONTRIBUTING.md#reporting-a-bug

### Current Behavior

On Android, when TalkBack or a screen reader is enabled and a popup opens, the screen reader's focus is placed on the general popup window, reading all the text and semantic properties, but it does not allow you to focus on individual elements of the pop-up, only on the buttons or `Entry` for example.

https://github.com/user-attachments/assets/0b6e33a0-c761-4ac9-a6a2-4f10dcaa6ee1

### Expected Behavior

Be able to click or navigate through the elements of the popup with the screen reader, just like in iOS.

### Steps To Reproduce

1. Enable TalkBack or the screen reader in an Android phone.
2. Open the app from the repro project.
3. Click to open any of the popups.
4. Try to click any content of the popup to focus the screen reader.
5. Try to click the buttons or the Entry of the popup to focus the screen reader.

### Link to public reproduction project repository

https://github.com/FabriBertani/PopupV2TalkBackBugRepro

### Environment

```markdown
- .NET MAUI CommunityToolkit: 12.2.0
- OS: Windows 11, Mac OS 15.6
- .NET MAUI: 9.0.90
```

### Anything else?

I believe this is related to the fact that the new popups are actually a `ContentPage` navigated as a modal, which is why the screen reader tends to focus on the entire screen rather than the popup contents.

Start with the linked PopupV2TalkBackBugRepro project and reproduce the behavior on Android with TalkBack enabled. Trace the Popup V2 ContentPage modal flow, compare its focus behavior with iOS, and verify that individual popup elements can be navigated and focused rather than only the window, buttons, or Entry.

Written by the indexing model from the issue text.