[UI] Standardize Welcome Modal Layout for Better UX

[mohammad-mghn]

Is there an existing issue that is already proposing this?

• I have searched the existing issues

🪄 describe your feature or idea

The position of the "Next" button changes when users interact with different parts of the modal, which can be frustrating. To improve the user experience during onboarding, we can standardize the size of all modals and keep the "Next" button in the same position across steps. like other website and applications.