Update README.md

Update README and courtroom portal documentation for improved clarity

Revised the README to reflect the correct path for the courtroom portal launcher and updated instructions for transcript viewing and exporting. Added a new section for spectators in the README and ensured consistent directory structure references throughout the documentation. Enhanced the courtroom portal README with detailed usage instructions and clarified the directory structure for better user navigation.

Add new models to OPENROUTER_MODELS list

Create SECURITY.md for security policy

Add a security policy document outlining supported versions and vulnerability reporting.