feat: animated landing page with scroll effects and terminal demo

[sagar-grv]

What's new

• Animated gradient mesh — drifting orbs and animated background gradient
• Scroll progress bar — shows reading progress at top of page
• Staggered reveal animations — sections and cards fade/slide in on scroll
• Parallax hero — subtle depth effect on hero orbs as you scroll
• Nav highlight — active section tracked in nav
• Dashboard stat counters — animated number counters triggered on visibility
• Terminal typing animation — step-by-step output simulation
• Install tabs — npm/pnpm/yarn/bun tab switcher
• FAQ accordion — smooth open/close animation
• Copy-to-clipboard — hero command and CTA with toast notification
• Mobile menu with close on link click

Zero CDN dependencies. Pure CSS + vanilla JS. Progressive enhancement.