fix(homepage): add overflow hidden to Your Journey section

Prevents the level slider from causing horizontal overflow on mobile
devices, which was making the page width wider than intended.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

apps/web/src/app/page.tsx

@@ -397,7 +397,7 @@ export default function HomePage() {
             </section>
 
             {/* Progression Visualization */}
-            <section className={stack({ gap: '6', mb: '16' })}>
+            <section className={stack({ gap: '6', mb: '16', overflow: 'hidden' })}>
               <div className={css({ textAlign: 'center' })}>
                 <h2
                   className={css({