Replace privacy popup with PrivacyModal and reorganize auth UI components
Remove signed-out persistence and centralize session handling in useAuthSession
Move document viewers and Kokoro voice helpers into dedicated modules
- Add device ID and IP-based rate limiting to prevent abuse
- Refactor UI components for better header menus and settings
- Update privacy popup with detailed data usage info
- Improve PDF handling and caching to prevent react-pdf warnings
- Update README with new Docker instructions and environment variables