Add Frontend/UI/UX/Design section with shadcn/ui
- Create dedicated frontend-ui-ux-design directory
- Add component libraries reference (shadcn/ui, Radix, MUI, etc.)
- Add design systems reference (Material, Carbon, Polaris)
- Add CSS frameworks reference (Tailwind, Bootstrap, CSS-in-JS)
- Add frontend stacks reference (React, Vue, Next.js, Svelte)
- Add UI experts reference (MiniMax, GLM design agents)
- Update README with prominent Frontend section
- Include shadcn/ui quick start guide
- Add recommended 2026 tech stack
