Replace ASCII art banners with mobile-responsive headers

- Replace fixed-width ASCII banners with CSS-styled section headers
- Add responsive styling for mobile devices
- Update home page, event pages, header and footer layouts
- Improve mobile experience with scalable headers and gradient dividers

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

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

layouts/_partials/footer.html

@@ -1,8 +1,4 @@
-<div class="ascii-border">
-<pre>
-+===================================================================+
-</pre>
-</div>
+<div class="footer-divider"></div>
 <p class="prompt">NERDER.LAND {{ now.Year }} - Connecting the tech underground</p>
 <p style="margin-top: 1rem; font-size: 0.8rem;">
   <a href="{{ "events/feed.xml" | absURL }}">📡 RSS Feed</a> |