feat(backend): integrate Redis workers, persistent model caching, Cohere V2 fallback, and 5x TTFT fast-path RAG

feat: implement Redis session memory and multi-turn conversational RAG with coreference resolution

feat(deploy): release Support Docs Copilot for Hugging Face Spaces

feat: implement JWT authentication with role-based access

feat: add auth guardrails and request observability

feat: add production config and readiness checks

feat: add FastAPI chat endpoints and streaming response support