Document technical choices and system architecture decisions

[NicolasLMP]

Why:
As a developer and stakeholder, I need comprehensive documentation of technical choices made in the Isschat project to ensure knowledge transfer, facilitate onboarding, and support future architectural decisions.

DoD:

• Document RAG pipeline technical architecture
• Explain technology stack choices (Streamlit, FAISS, OpenRouter, etc.)
• Document evaluation system design decisions
• Add database and storage architecture documentation
• Document API integrations and authentication choices
• Create deployment and infrastructure documentation
• Add troubleshooting guide for common issues
• Review documentation completeness with team

How:

• Create comprehensive architecture documentation in project wiki
• Document decision rationale for major technology choices
• Add system diagrams and component interaction flows
• Document configuration and environment setup procedures
• Create troubleshooting guides for known issues
• Add performance considerations and optimization notes
• Review documentation with team for accuracy and completeness
• Keep documentation updated with system changes