Fix Vercel routing for demo fetch request

Changed fetch URL from 'get.php' to './get.php' to ensure relative path
resolution. When deployed at /example, the request now correctly resolves
to /example/get.php instead of /get.php (root).

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: eypsilon

example/index.html

@@ -1269,7 +1269,7 @@ <h3 style="margin-bottom: 0.5rem;">⚡ Powered by YEH</h3>
                 messagesContainer.style.display = 'none';
 
                 try {
-                    const response = await fetch('get.php', {
+                    const response = await fetch('./get.php', {
                         method: 'POST',
                         body: new FormData(form)
                     });