Fix footer button layout on mobile

Make footer navigation buttons responsive:
- Stack vertically on mobile with full-width buttons
- Horizontal layout with space-between on desktop
- Add consistent gap-4 spacing between buttons
- Improve touch targets on mobile devices

Author: saadshahd

src/pages/portfolio/statsbomb.mdx

@@ -762,11 +762,11 @@ The human side of building production systems: our team in Cairo (2018-2022), wh
   <hr class="border-neutral-light my-8" />
 
   {/* Footer Navigation */}
-  <div class="flex justify-between items-center">
-    <Button variant="secondary" href="/portfolio">
+  <div class="flex flex-col md:flex-row gap-4 md:justify-between md:items-center">
+    <Button variant="secondary" href="/portfolio" class="w-full md:w-auto">
       ← Back to Portfolio
     </Button>
-    <Button variant="primary" href="/contact">
+    <Button variant="primary" href="/contact" class="w-full md:w-auto">
       Start a Conversation →
     </Button>
   </div>