Add Dark/Light Theme Toggle Animation

The theme toggle works but needs a smooth transition animation between themes.

Acceptance Criteria:

• Add smooth transition when switching themes
• Animate the toggle button itself
• Ensure all colors transition smoothly
• Maintain neon green accent in both themes

Implementation Hints:

• Check ThemeToggle.tsx and ThemeContext.tsx
• Use CSS transitions or Tailwind's transition classes
• Consider adding a sun/moon icon animation