Use theme-based styles in ConfigureAndUploadDatasetStep

[Irozuku]

Summary

Refactors the ConfigureAndUploadDatasetStep component to use theme-based styles instead of hardcoded values, improving visual consistency and maintainability across the application.

Before

After

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Type of Change

Check all that apply like this [x]:

• Backend change
• Frontend change
• CI / Workflow change
• Build / Packaging change
• Bug fix
• Documentation

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Changes (by file)

• ConfigureAndUploadDatasetStep.tsx:
  • Replaced hardcoded background color and padding with values from the MUI theme (theme.palette.background.box and adjusted spacing).
  • Added useTheme hook to access and apply theme variables.

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Testing (optional)

• Verify that the component renders correctly in both light and dark modes.