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/monitoring/src/cloudwatch.ts

@@ -0,0 +1,97 @@
+import { CloudWatchClient, PutMetricDataCommand, StandardUnit } from '@aws-sdk/client-cloudwatch';
+import { getMonitoringConfig } from './config';
+
+let client: CloudWatchClient | null = null;
+
+function getClient(): CloudWatchClient | null {
+  if (client) return client;
+
+  const config = getMonitoringConfig();
+  const region = process.env.AWS_REGION || 'us-east-1';
+
+  try {
+    client = new CloudWatchClient({ region });
+    return client;
+  } catch {
+    console.warn('[CloudWatch] Metrics client initialization skipped');
+    return null;
+  }
+}
+
+export interface MetricDataPoint {
+  MetricName: string;
+  Dimensions?: { Name: string; Value: string }[];
+  Value: number;
+  Unit?: string;
+  Timestamp?: Date;
+}
+
+const NAMESPACE = 'ShieldAI';
+
+export async function emitMetric(
+  serviceName: string,
+  metricName: string,
+  value: number,
+  unit: StandardUnit = 'Count',
+  dimensions?: Record<string, string>
+) {
+  const cw = getClient();
+  if (!cw) return;
+
+  const dims: { Name: string; Value: string }[] = [
+    { Name: 'service', Value: serviceName },
+    ...(dimensions ? Object.entries(dimensions).map(([n, v]) => ({ Name: n, Value: v })) : []),
+  ];
+
+  const command = new PutMetricDataCommand({
+    Namespace: NAMESPACE,
+    MetricData: [
+      {
+        MetricName: metricName,
+        Dimensions: dims,
+        Value: value,
+        Unit: unit,
+      },
+    ],
+  });
+
+  try {
+    await cw.send(command);
+  } catch (err) {
+    console.warn('[CloudWatch] Metric emit failed:', (err as Error).message);
+  }
+}
+
+export async function emitLatency(
+  serviceName: string,
+  latencyMs: number,
+  percentile: 'p50' | 'p95' | 'p99'
+) {
+  await emitMetric(
+    serviceName,
+    'api_latency',
+    latencyMs,
+    'Milliseconds' as StandardUnit,
+    { percentile }
+  );
+}
+
+export async function emitRequestCount(serviceName: string, statusCode: number) {
+  await emitMetric(
+    serviceName,
+    'api_requests',
+    1,
+    'Count' as StandardUnit,
+    { status_class: String(Math.floor(statusCode / 100)) + 'xx' }
+  );
+}
+
+export async function emitError(serviceName: string, errorType: string) {
+  await emitMetric(
+    serviceName,
+    'api_errors',
+    1,
+    'Count' as StandardUnit,
+    { error_type: errorType }
+  );
+}