Add micro animation to search expansion

Commit notes

- Add smooth width transition with ease-out-cubic easing (220ms) - Add subtle scale animation when expanding (0.98 to 1) - Add content fade-in with slight translateX motion for polish - Use will-change for GPU acceleration on width and transform - Add proper prefers-reduced-motion support for accessibility - Follow animation guidelines with fast, purposeful motion

Co-authored-by: armin.naimi <[email redacted]>