feat: redesign landing page with aurora background

Major landing page redesign with simplified content and animated background:

- Added aurora background component with animated gradient effect
- Simplified hero section and streamlined messaging
- Removed scroll-reveal card animations for better performance
- Reorganized feature cards for better user flow
- Centered governance section cards
- Added CSS animations for aurora effect in globals.css
- Cleaned up unnecessary sections and redundant content

Files changed:
- src/components/pages/homepage/index.tsx: Complete page restructure
- src/components/ui/background.tsx: New aurora background component
- src/styles/globals.css: Added aurora animation keyframes

Author: christiangruender