Fix unit test compatibility and train/load RAC model artifacts

feat(fixes): replace agent core implementation and test suites with real behavior

fix(backend): resolve type checking errors and name reuse conflicts

style: run ruff format on backend app files

fix: resolve ruff lint errors in backend

feat: implement database audit guard, WebSocket telemetry, rate limiter, outgoing call capper, and system status health check

deploy: Hugging Face Spaces backend