test(security): add ActuatorSecurityTest to guard auth boundaries

Tests that /actuator/health is accessible without credentials and
/actuator/env requires authentication — permanent regression guards
against CVE-2026-40976-class Actuator filter chain bypass bugs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/test/java/org/raddatz/familienarchiv/ActuatorSecurityTest.java

@@ -0,0 +1,55 @@
+package org.raddatz.familienarchiv;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.web.server.LocalManagementPort;
+import org.springframework.context.annotation.Import;
+import org.springframework.http.ResponseEntity;
+import org.springframework.test.context.ActiveProfiles;
+import org.springframework.test.context.bean.override.mockito.MockitoBean;
+import org.springframework.web.client.DefaultResponseErrorHandler;
+import org.springframework.web.client.RestTemplate;
+import software.amazon.awssdk.services.s3.S3Client;
+
+import java.io.IOException;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
+@ActiveProfiles("test")
+@Import(PostgresContainerConfig.class)
+class ActuatorSecurityTest {
+
+    @LocalManagementPort
+    private int managementPort;
+
+    @MockitoBean
+    S3Client s3Client;
+
+    @Test
+    void actuator_health_is_accessible_without_authentication() {
+        ResponseEntity<String> response = noThrowTemplate().getForEntity(
+                "http://localhost:" + managementPort + "/actuator/health", String.class);
+
+        assertThat(response.getStatusCode().value()).isEqualTo(200);
+    }
+
+    @Test
+    void actuator_env_requires_authentication() {
+        ResponseEntity<String> response = noThrowTemplate().getForEntity(
+                "http://localhost:" + managementPort + "/actuator/env", String.class);
+
+        assertThat(response.getStatusCode().value()).isEqualTo(401);
+    }
+
+    private RestTemplate noThrowTemplate() {
+        RestTemplate template = new RestTemplate();
+        template.setErrorHandler(new DefaultResponseErrorHandler() {
+            @Override
+            public boolean hasError(org.springframework.http.client.ClientHttpResponse response) throws IOException {
+                return false;
+            }
+        });
+        return template;
+    }
+}