Update Footer component to use semantic color variables for better theme integration:
- Replace hardcoded background color with semi-color-bg-2 for theme consistency
- Update text colors to use semantic variables (semi-color-text-0, semi-color-text-1)
- Replace hardcoded link colors with semi-color-primary for brand consistency
- Add hover effects with smooth transitions for better user experience
- Keep logo container background as gray-800 for visual stability
This ensures the footer adapts properly to different theme modes while maintaining
good readability and visual consistency across the application.
