feat: responsive system, engineering infra, new components, performance

- Section: responsive prop with media query injection
- visual-weights: fontSize clamp() for responsive sizing
- variables.css: add border-radius/shadow/transition/z-index tokens
- ESLint flat config + Prettier + Changeset init
- New components: Footer, NewsSidebar, BreakingNewsBanner
- Image/Figure: loading=lazy, aspectRatio, sizes props

packages/docs/app/blocks/zh-frontpage/page.tsx

@@ -1,5 +1,5 @@
 'use client';
-import { Layout, Section, Article, Rule, BodyText, Figure } from '@newspaperui/components';
+import { Layout, Section, Article, Rule, BodyText, Figure } from 'newspaperui-components';
 
 const cn = { fontFamily: 'var(--font-family-cjk-serif)' };
 const cnRed = { color: 'var(--nui-accent-cjk-red)' };