enhance rag

feat: Hardened routing layer with Redis-backed rate limiting, distributed circuit breakers, bulkheads, and full OTel/Prom observability with Grafana alerts

fix(core): remove broken router pre-flight checks, secure auth bypass, and update OpenRouter config

feat: implement v4 resilient multi-provider LLM routing with smart scoring, circuit breakers, self-healing, dynamic models, and rate limiting

fix(llm): resolve NameError in gemini_client, update provider model lists, and fix 503 error propagation

refactor(llm): implement resilient multi-provider router, add circuit breaker, update models, and enforce 503 HTTP failovers

feat: pass user access_token to .NET API for native authorization

feat: clean deployment with bug fixes and stability improvements