feat: add agent status and observability status endpoints

Implements AgentStatusService (TDD) that proxies cameleer3-server agent
registry API and queries ClickHouse for trace counts. Gracefully degrades
to UNKNOWN state when server is unreachable or DataSource is absent.

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

src/test/java/net/siegeln/cameleer/saas/observability/AgentStatusServiceTest.java

@@ -0,0 +1,92 @@
+package net.siegeln.cameleer.saas.observability;
+
+import net.siegeln.cameleer.saas.app.AppEntity;
+import net.siegeln.cameleer.saas.app.AppRepository;
+import net.siegeln.cameleer.saas.environment.EnvironmentEntity;
+import net.siegeln.cameleer.saas.environment.EnvironmentRepository;
+import net.siegeln.cameleer.saas.runtime.RuntimeConfig;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import java.util.Optional;
+import java.util.UUID;
+
+import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.*;
+
+@ExtendWith(MockitoExtension.class)
+class AgentStatusServiceTest {
+
+    @Mock private AppRepository appRepository;
+    @Mock private EnvironmentRepository environmentRepository;
+    @Mock private RuntimeConfig runtimeConfig;
+
+    private AgentStatusService agentStatusService;
+
+    @BeforeEach
+    void setUp() {
+        when(runtimeConfig.getCameleer3ServerEndpoint()).thenReturn("http://localhost:9999");
+        agentStatusService = new AgentStatusService(appRepository, environmentRepository, runtimeConfig);
+    }
+
+    @Test
+    void getAgentStatus_appNotFound_shouldThrow() {
+        when(appRepository.findById(any())).thenReturn(Optional.empty());
+        assertThrows(IllegalArgumentException.class,
+                () -> agentStatusService.getAgentStatus(UUID.randomUUID()));
+    }
+
+    @Test
+    void getAgentStatus_shouldReturnUnknownWhenServerUnreachable() {
+        var appId = UUID.randomUUID();
+        var envId = UUID.randomUUID();
+
+        var app = new AppEntity();
+        app.setId(appId);
+        app.setEnvironmentId(envId);
+        app.setSlug("my-app");
+        when(appRepository.findById(appId)).thenReturn(Optional.of(app));
+
+        var env = new EnvironmentEntity();
+        env.setId(envId);
+        env.setSlug("default");
+        when(environmentRepository.findById(envId)).thenReturn(Optional.of(env));
+
+        // Server at localhost:9999 won't be running — should return UNKNOWN gracefully
+        var result = agentStatusService.getAgentStatus(appId);
+
+        assertNotNull(result);
+        assertFalse(result.registered());
+        assertEquals("UNKNOWN", result.state());
+        assertEquals("my-app", result.applicationId());
+        assertEquals("default", result.environmentId());
+    }
+
+    @Test
+    void getObservabilityStatus_shouldReturnEmptyWhenClickHouseUnavailable() {
+        var appId = UUID.randomUUID();
+        var envId = UUID.randomUUID();
+
+        var app = new AppEntity();
+        app.setId(appId);
+        app.setEnvironmentId(envId);
+        app.setSlug("my-app");
+        when(appRepository.findById(appId)).thenReturn(Optional.of(app));
+
+        var env = new EnvironmentEntity();
+        env.setId(envId);
+        env.setSlug("default");
+        when(environmentRepository.findById(envId)).thenReturn(Optional.of(env));
+
+        // No ClickHouse DataSource injected — should return empty status
+        var result = agentStatusService.getObservabilityStatus(appId);
+
+        assertNotNull(result);
+        assertFalse(result.hasTraces());
+        assertEquals(0, result.traceCount24h());
+    }
+}