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: add multi-turn conversation memory

feat: add LLM-based query rewriting

fix: normalize logging, error handling, and streaming consistency

feat: add auth guardrails and request observability

feat: add cited answers and configurable retrieval

feat: add multi-format ingestion and index lifecycle

feat: add production config and readiness checks

feat: implement hybrid document ingestion with Qdrant and FastEmbed