test(admin): U10 — E2E + security isolation + quota enforcement tests
23 integration tests across 3 files:
- test_e2e_admin_flow: 5 end-to-end lifecycle tests (department, user,
LLM config, skill management, usage dashboard)
- test_security_isolation: 7 department isolation tests + non-admin 403
tests (cross-dept skill/KB access, multi-dept union, admin sees all,
removed user loses access, disabled dept, API key client)
- test_quota_enforcement: 10 quota tests (token/cost/whitelist limits,
multi-dept strictest-wins, real gateway integration, usage recording)
418 admin tests pass, no regressions.