feat(phase-9): implement MVP polishing and closure
T-032: User management admin panel - backend users router with CRUD, frontend UsersPage with modals
T-033: Audit log viewer - backend audit router with filters/pagination, frontend AuditLogPage
T-034: Global error handling - ErrorBoundary, LoadingSpinner, ErrorMessage, Toast components
T-035: Backend tests - pytest setup with SQLite, tests for health/auth/techniques/tests
T-036: Documentation - Updated README with testing section, created docs/API.md