feat: async pipeline, job queue, generation hardening, and docs

feat: adaptive writing style — user docs first, KB fallback, few-shot examples

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

- Introduced a new API endpoint for finding similar content in the tenant's workspace, allowing users to identify overlapping uploads and draft notes.

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

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

fix: resolve startup and background task issues for Python 3.13 + Starlette 0.52

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