Update RAG resources link and fix homepage formatting issues

[jxnl]

Updates needed for RAG resources section

Changes needed:

1. Replace existing RAG materials/resources section with a link to the comprehensive guide: https://567-labs.github.io/systematically-improving-rag/

2. Review and fix formatting issues on the homepage - there appear to be display/layout problems that need attention.

Priority:

Medium

Notes:

The systematically-improving-rag site should be the central resource for all RAG-related content, so we should direct visitors there instead of maintaining separate resources in multiple places.