- Add @Order(1) managementFilterChain scoped to /actuator/** with explicit
401 entry point, blocking all non-public actuator paths without the
form-login redirect that the main chain uses for browser clients.
- Split single combined test into two focused assertions
(prometheus_endpoint_returns_200_without_credentials,
prometheus_endpoint_returns_jvm_metrics).
- Add negative regression test: actuator_metrics_requires_authentication
verifies that /actuator/metrics returns 401 without credentials.
Addresses reviewer concerns from @sara (missing negative test, split
assertions) and @nora (dedicated management security layer).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>