Wire up remaining TODO stubs: P3 test notifications, P2 drift notification trigger

- P3: test notification endpoint now instantiates real Slack/Email/Webhook notifiers
- P2: drift processor triggers notification service when drift_score > 0 (non-fatal on failure)

products/02-iac-drift-detection/saas/src/processor/routes.ts

@@ -56,8 +56,21 @@ export async function registerProcessorRoutes(app: FastifyInstance) {
       );
     });
 
-    // TODO: Trigger notification if drift_score > threshold
-    // TODO: Trigger remediation workflow if auto-remediate enabled
+    // Trigger notification if drift score exceeds threshold
+    if (report.drift_score > 0) {
+      try {
+        const { DriftNotificationService } = await import('../notifications/service.js');
+        const notifService = new DriftNotificationService(pool);
+        await notifService.notifyDrift(tenantId, {
+          stackName: report.stack_name,
+          driftScore: report.drift_score,
+          totalResources: report.total_resources,
+          driftedResources: report.drifted_resources?.length ?? 0,
+        });
+      } catch (err) {
+        app.log.warn({ tenantId, error: (err as Error).message }, 'Notification dispatch failed (non-fatal)');
+      }
+    }
 
     return reply.status(201).send({ status: 'accepted' });
   });