feat: revamp site with Vite, Tailwind v4, React 19, pnpm

[wemeetagain]

Summary

• Build: Webpack → Vite (instant dev server, 10-line config vs 70)
• Styling: Bulma/SCSS → Tailwind CSS v4 (dark-mode-first, utility classes)
• Framework: React 18 → React 19 with createRoot
• Toasts: react-hot-toast → sonner
• Package manager: yarn → pnpm
• ENR lib: @chainsafe/enr v5 → v6
• UI: Auto-decode on paste/type, copy-to-clipboard on all fields, staggered field animations, proper a11y, responsive layout
• CI: Updated workflows for pnpm, bumped actions/setup-node to v4

Net: -2,084 lines (removed webpack config, Bulma SCSS, yarn.lock)

Test plan

• pnpm dev starts dev server and renders correctly
• Paste an ENR string — auto-decodes without clicking a button
• All decoded fields display with copy buttons on hover
• Derived fields (node id, peer id, multiaddrs) compute and display
• URL query param ?q=enr:... loads and decodes on page load
• File upload populates textarea and decodes
• Invalid ENR shows error toast
• pnpm build produces working production build
• pnpm lint and pnpm check-types pass clean

🤖 Generated with Claude Code