docs: update demo video link in README

Replace demo video link with new version and preserve old link in comment for reference.

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

Author: Dumbris

README.md

@@ -4,7 +4,8 @@
 
 ### **📚 [Read the Documentation](https://docs.mcpproxy.app/)**
 
-[![MCPProxy Demo](https://img.youtube.com/vi/l4hh6WOuSFM/0.jpg)](https://youtu.be/l4hh6WOuSFM)
+<!-- Old video: https://youtu.be/l4hh6WOuSFM -->
+[![MCPProxy Demo](https://img.youtube.com/vi/2aKrgJnbbcw/0.jpg)](https://youtu.be/2aKrgJnbbcw)
 
 <a href="https://mcpproxy.app" target="_blank" rel="noopener">🌐 Visit mcpproxy.app</a>