feat: Implement foundational UI components (Button, Card) and layout components (Section, Container), updating design tokens, styling, and documentation.

app/page.tsx

@@ -1,7 +1,14 @@
+import { Container } from "@/components/layout/Container";
+import { Section } from "@/components/layout/Section";
+
 export default function Page() {
   return (
     <main>
-      <p>Ready</p>
+      <Section>
+        <Container>
+          <p>Ready</p>
+        </Container>
+      </Section>
     </main>
   );
 }