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

.prettierignore

@@ -0,0 +1,5 @@
+dist
+out
+.next
+node_modules
+pnpm-lock.yaml