Upgrade Next.js and React to latest stable versions; migrate middleware to proxy; update TS tooling in cuicui monorepo

[cto-new]

Summary

Upgrade Next.js to the latest stable version and React/React DOM to the latest stable versions across the cuicui monorepo. Align config and tooling with the new Next.js 16 conventions and ensure the website builds and tests pass.

Details

• Upgrade Next.js to 16.x and React / React DOM to 19.x across apps (website) and dependencies
• Migrate Next.js 16 breaking changes: move reactCompiler to top-level, rename middleware.ts to proxy.ts and adjust usage
• Update tsconfig.json and next-env.d.ts to reflect new JSX runtime and typings
• Update ESLint config to Next.js 16 compatibility; adjust any lint issues
• Add placeholder env vars via .env.local to allow build to proceed in CI
• Verify pnpm build across workspaces and run Vitest tests; ensure server starts without errors