feat: enhance embedding model configuration and retrieval logic

feat: introduce strict uploaded only mode and enhance logging for AI generation

feat: enhance AI involvement handling and transparency metrics

- Added support for RICS survey levels (1, 2, 3) in document uploads and reports, allowing for better tier management and retrieval filtering.

- Replaced timezone.utc with UTC from datetime for consistent datetime handling.

feat(experiment-lab): AI transparency bar, tenant-scoped RAG, citations, proofread/enhance fixes