docs: add comprehensive environment variables reference and update configuration
- Add new environment_variables.md with complete reference table and use case guides
- Update configuration.md table with default values and new variables
- Add CAI_GUARDRAILS, CAI_MAX_INTERACTIONS, CAI_STREAM, CAI_TELEMETRY, CAI_PARALLEL, CAI_GCTR_NITERATIONS, CAI_ACTIVE_CONTAINER
- Organize variables by use case: Getting Started, CTF, Memory, Security, Performance, Advanced, Container, TUI
- Add practical examples for common configurations
- Update mkdocs.yml navigation to include Environment Variables in Guides section
danielsanchezprieto01