## Changes
### Sidebar
- Remove hardcoded `backgroundColor: "#000000"`
- Use `theme.palette.background.main` for dynamic theming
- Update border color to use `theme.palette.border.light`
### Body Background
- Remove hardcoded `background-color: #000000` from index.css
- Add GlobalStyles in App.jsx to apply theme background to body element
## Benefits
- Sidebar now properly displays in light mode
- Body background adapts correctly to theme changes
- Consistent theming across light and dark modes