refactor(ui): rewrite Heading component to act as central typography system, fix line-heights, and apply to MDX pages

Former-commit-id: dc62485b60679b810b5f74bfb5a22915b7a62314

app/[locale]/page.tsx

@@ -13,6 +13,7 @@ import { CompetenceBentoGrid as HomeCompetenceBentoGrid } from '@/components/blo
 import { ReferencesSlider as HomeReferencesSlider } from '@/components/blocks/ReferencesSlider';
 
 import { Button } from '@/components/ui/Button';
+import { Heading } from '@/components/ui/Heading';
 
 const mdxComponents = {
   HomeHero,
@@ -20,6 +21,7 @@ const mdxComponents = {
   HomeCompetenceBentoGrid,
   HomeReferencesSlider,
   Button,
+  Heading,
 };
 
 export async function generateMetadata(props: any): Promise<Metadata> {