the border radius and the centering of the cupertino bottom sheet is not working in flet v0.26

[begeansma019]

Duplicate Check

• I have searched the opened issues and there are no duplicates

Describe the bug

In flet 0.25.2 the border radius and the centering of the Cupertino bottom sheet works :

but in the latest dev version flet==0.26.0.dev4041 the border radius can not be seen and the bottom sheet is being centered is not see that well because of the page being displayed under it :

Code sample

Code

import flet as ft


def main(page):
    page.horizontal_alignment = ft.CrossAxisAlignment.CENTER
    text= ft.Text(
                "Welcome to our application! We aim to provide the best services and solutions "
                "to meet your needs. Our team is dedicated to ensuring customer satisfaction and "
                "delivering exceptional results. Here's what we offer:\n\n"
                "- High-quality products\n"
                "- Reliable customer support\n"
                "- Continuous innovation\n"
                "- A commitment to excellence\n\n"
                "Thank you for choosing us. We look forward to serving you!",
                size=16,
                text_align=ft.TextAlign.JUSTIFY,
                font_family="Quicksand",  # Ensure font is specified
            ),

    text_fields_container = ft.Container(
        content=ft.Column(
            text,


            spacing=10,
            alignment=ft.MainAxisAlignment.CENTER,  # Center all elements vertically
            horizontal_alignment=ft.CrossAxisAlignment.CENTER,  # Center all elements horizontally
        ),
        border_radius=20,
        padding=30,

        bgcolor=ft.colors.WHITE,
    )

    bottom_sheet = ft.CupertinoBottomSheet(
        content=ft.Container(
            content=text_fields_container,
            padding=ft.Padding(0, 0, 0, 250),  # Add padding around the action sheet content
            width=500,  # Keep the desired width
            height=650
            ,
        ),
    )
    page.add(bottom_sheet)
    bottom_sheet.open = True
    page.update()

ft.app(main)



### To reproduce

Just run the code on a python IDE 

### Expected behavior

In the latest flet release  flet==0.26.0.dev4041 the border radius is not really seen and the centering of the bottom sheet can not be seen because of the page being displayed below it 



### Screenshots / Videos

<details open>
<summary>Captures</summary>

![Image](https://github.com/user-attachments/assets/9923c452-aef3-466c-86f1-66cb20d0cc1d)

</details>


### Operating System

Windows

### Operating system details

Version 23H2 OS Build 22631.4751

### Flet version

pip install flet==0.26.0.dev4041

### Regression

Yes, it used to work in a previous Flet version (please specify the version in additional details)

### Suggestions

_No response_

### Logs

<details open><summary>Logs</summary>

```console
[Paste your logs here]

Additional details

No response

[begeansma019]

Does any one know to change the logo on a dynamic flet app and how to change the splash screen ?