Ship production RAG hardening: citation extraction, full-library retrieval, auth.

Speed up generation and ingestion; add live report progress on /status.

- 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: FAISS-only vector store (remove Chroma)

- Introduced `ingest_timeout_seconds` setting in config.py to define maximum time for document ingestion.

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

feat: enhance document upload and processing capabilities with new personalisation features

fix: comprehensive codebase review fixes (critical + major + minor issues)

feat: add complete browser UI with upload, section config, generate and results views

feat: scaffold complete RAG system for RICS-style report generation