feat: integrate Datadog APM + Sentry error tracking with CloudWatch metrics FRE-4806

- Add CloudWatch metrics emitter (api_latency, api_requests, api_errors)
- Add request monitoring middleware for API (latency, error rate, throughput)
- Register error-handling, logging, and monitoring middleware in server.ts
- Add Datadog log forwarding via HTTP intake API
- Add application-level CloudWatch alarms for P99 latency, error rate, throughput
- Inject Datadog/Sentry env vars and secrets into ECS task definitions
- Add DD_API_KEY and SENTRY_DSN to ECS secrets
- Create CloudWatch log groups for datadog and sentry services
- Update .env.example with AWS_REGION and monitoring variables
- Add @aws-sdk/client-cloudwatch dependency to monitoring package

Co-Authored-By: Paperclip <noreply@paperclip.ing>

packages/api/src/middleware/monitoring.middleware.ts

@@ -0,0 +1,46 @@
+import { FastifyInstance, FastifyRequest, FastifyReply } from 'fastify';
+import { emitLatency, emitRequestCount, emitError } from '@shieldai/monitoring';
+
+const SERVICE_NAME = process.env.DD_SERVICE || 'shieldai-api';
+
+export async function monitoringMiddleware(fastify: FastifyInstance) {
+  fastify.addHook('onResponse', async (request: FastifyRequest, reply: FastifyReply) => {
+    const statusCode = reply.statusCode;
+    const responseTime = reply.elapsedTime;
+    const method = request.method;
+    const url = request.url;
+
+    // Emit request count
+    await emitRequestCount(SERVICE_NAME, statusCode);
+
+    // Emit latency metrics
+    await emitLatency(SERVICE_NAME, responseTime, 'p50');
+    await emitLatency(SERVICE_NAME, responseTime, 'p95');
+    await emitLatency(SERVICE_NAME, responseTime, 'p99');
+
+    // Emit error metric for 5xx
+    if (statusCode >= 500) {
+      await emitError(SERVICE_NAME, 'server_error');
+      fastify.log.warn({
+        event: 'high_latency_or_error',
+        method,
+        url,
+        statusCode,
+        responseTime,
+        service: SERVICE_NAME,
+      });
+    }
+
+    // Log high latency requests (>2s)
+    if (responseTime > 2000) {
+      fastify.log.warn({
+        event: 'high_latency',
+        method,
+        url,
+        statusCode,
+        responseTime,
+        service: SERVICE_NAME,
+      });
+    }
+  });
+}