[OPIK-7159] test: assert reaper job is Guice-constructible (@config wiring)

Self-review gap: the reaper-job unit test constructs the job with `new`, so it never
exercised the Guice/Quartz @config("optimizationStalledReaper") injection — which is the
exact fragility the explicit-@Inject-ctor change guards against. Add an injector
resolution assertion (reusing the reaper service test's booted app) so a broken @config
qualifier fails the build.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: awkoy

apps/opik-backend/src/test/java/com/comet/opik/domain/OptimizationStalledReaperServiceTest.java

@@ -13,10 +13,12 @@
 import com.comet.opik.api.resources.utils.TestUtils;
 import com.comet.opik.api.resources.utils.WireMockUtils;
 import com.comet.opik.api.resources.utils.resources.OptimizationResourceClient;
+import com.comet.opik.api.resources.v1.jobs.OptimizationStalledReaperJob;
 import com.comet.opik.extensions.DropwizardAppExtensionProvider;
 import com.comet.opik.extensions.RegisterApp;
 import com.comet.opik.podam.PodamFactoryUtils;
 import com.google.common.eventbus.EventBus;
+import com.google.inject.Injector;
 import com.redis.testcontainers.RedisContainer;
 import org.apache.commons.lang3.RandomStringUtils;
 import org.junit.jupiter.api.BeforeAll;
@@ -120,18 +122,29 @@ class OptimizationStalledReaperServiceTest {
 
     private OptimizationResourceClient optimizationResourceClient;
     private OptimizationService optimizationService;
+    private Injector injector;
 
     @BeforeAll
-    void beforeAll(ClientSupport client, OptimizationService optimizationService) {
+    void beforeAll(ClientSupport client, OptimizationService optimizationService, Injector injector) {
         var baseURI = TestUtils.getBaseUrl(client);
         ClientSupportUtils.config(client);
 
         this.optimizationResourceClient = new OptimizationResourceClient(client, baseURI, podamFactory);
         this.optimizationService = optimizationService;
+        this.injector = injector;
 
         mockTargetWorkspace(wireMock.server(), API_KEY, TEST_WORKSPACE_NAME, WORKSPACE_ID, USER);
     }
 
+    @Test
+    @DisplayName("reaper job is constructible via Guice (@Config qualifier wiring)")
+    void reaperJobIsInjectableFromGuice() {
+        // The reaper is disabled/unscheduled in config-test.yml, but the bean is still bound — so this
+        // proves the explicit @Inject constructor + @Config("optimizationStalledReaper") qualifier wire
+        // correctly at boot (the Quartz/Guice fragility the explicit-ctor change guards against).
+        assertThat(injector.getInstance(OptimizationStalledReaperJob.class)).isNotNull();
+    }
+
     static Stream<Arguments> stalledRuns() {
         return Stream.of(
                 // INITIALIZED matched by the initialized branch (running timeout kept long so only the