Add comprehensive documentation for Linear Void project

- Created README.md in docs folder outlining project structure and documentation links.
- Added SECURITY.md detailing the security model, threat model, authentication, transport security, network isolation, and incident response procedures.
- Introduced SETUP.md providing a detailed setup guide for local and production environments, including prerequisites, environment setup, and Gitea integration.
- Added STREAMING.md outlining the streaming pipeline, including production flow, source-media contract, playout and HLS packaging, cache contract, player behavior, and monitoring.
- Updated architecture documentation to include links to new SETUP.md and STREAMING.md files for better navigation.

docs/README.md

@@ -0,0 +1,41 @@
+# Docs Folder
+
+This folder contains the documentation for the Linear Void project. The documentation is organized into several markdown files, each covering different aspects of the project.
+
+## Architecture
+
+- [Architecture](architecture/README.md) - High-level system architecture and component interactions.
+
+## API
+
+- [API](API.md) - Implemented WebSocket and REST API reference.
+
+## Deployment
+
+- [Deployment](DEPLOYMENT.md) - Production deployment and operational runbook.
+
+## Monitoring
+
+- [Monitoring](MONITORING.md) - Metrics, dashboards, and monitoring troubleshooting.
+
+## Security
+
+- [Security](SECURITY.md) - Security model, controls, and hardening baseline.
+
+## Setup
+
+- [Setup](SETUP.md) - Test lab setup, local development, and CI/CD workflow.
+
+## Streaming
+
+- [Streaming](STREAMING.md) - Streaming architecture, playout, and delivery details.
+
+## Development
+
+- [Development](DEVELOPMENT.md) - Remaining tasks and test fixtures for development.
+
+## Additional Resources
+
+- [Marketing](marketing/README.md) - Marketing materials and resources.
+- [Operations](operations/README.md) - Operational procedures and checklists.
+- [Incident Runbook](incident-runbook.md) - Incident response and disaster recovery procedures.