Add certificate images for new participants and fix image generation script

- Generated certificate images for Neha, Muhammad Zeeshan, and Subash Natarajan
- Fixed deprecated puppeteer waitForTimeout API usage
- Regenerated all certificate images with updated script
- Images now available for LinkedIn/Twitter social media previews

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

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

Author: 2 people