fix: prevent invalid form controls from blanking pages

[mytharcher]

Summary

• Document the required Base UI FormControl render={...} composition for coding agents.
• Require the render prop and reject FormControl children at TypeScript compile time.
• Add a localized page error boundary with reload and homepage recovery actions.

Testing

• ./node_modules/.bin/tsc --noEmit (clean archive of HEAD)
• pnpm exec eslint src/App.tsx src/components/ui/form.tsx src/components/app-shell/page-error-boundary.tsx src/locales/en-US.ts src/locales/zh-CN.ts
• pnpm exec vite build

ESLint completed with the existing Fast Refresh warning in src/components/ui/form.tsx and no errors.

Changelog

• Prevented invalid form control composition from silently reaching production and added a recovery page for rendering errors.
• 阻止无效的表单控件组合静默进入生产环境，并为页面渲染错误增加恢复页面。