fix: Python 3.10 compat — replace datetime.UTC with timezone.utc shim

feat: WebLLM browser agent with PeerJS mesh, HybridRAG, news signals, and easter-egg ticker

feat: federated RAG + comprehensive security fixes

fix: Python 3.10 compatibility for HF Space (Python 3.10 env)

fix: 0 test failures; FileService; real RagService; emergency probe; chat return

feat: implement all M01-M13, X01-X04 modules + quality gate fixes