Update the body/container background that match the SVG background

Current live preview 
 
<img width="646" height="546" alt="Image" src="https://github.com/user-attachments/assets/8ffbb012-fa03-427a-a051-6dc101204a4e" />


Expected preview that match with theme background 

<img width="652" height="488" alt="Image" src="https://github.com/user-attachments/assets/bb2fa2d5-4d4f-4c1c-b936-3b45c2d34b68" />
