Applied the same web_ui.html path fix to backend/api_server.py that
was previously applied to the root api_server.py. The backend version
needs to reference the parent directory since web_ui.html is located
at /opt/ai_qc/web_ui.html while api_server.py is in /opt/ai_qc/backend/.
This fixes the 404 error when running via Waitress production server.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>