Add load testing job to GitHub Actions CI pipeline (FRE-4931)

- Add load-test job to ci.yml that runs after docker-build on push to main
- Create combined load test runner (scripts/load-test/run-all.sh) for all services
- Create k6 load test scripts for api, darkwatch, spamshield, and voiceprint
- Add shared k6 utilities (lib/common.js)
- Update load-test.yml to support all services and report artifacts
- Configure k6 cloud output and P99 threshold validation
- Generate load test report as CI artifact

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

scripts/load-test/services/api.js

@@ -0,0 +1,48 @@
+import http from 'k6/http';
+import { check, group } from 'k6';
+import { Rate, Trend } from 'k6/metrics';
+import { getBaseUrl, getTargetRps, getDuration, defaultThresholds, checkResponse, randomString } from '../lib/common.js';
+
+const errorRate = new Rate('errors');
+const notificationLatency = new Trend('notification_p99');
+const correlationLatency = new Trend('correlation_p99');
+
+export const options = {
+  thresholds: {
+    ...defaultThresholds(250).thresholds,
+    notification_p99: ['p(99)<500'],
+    correlation_p99: ['p(99)<300'],
+  },
+};
+
+const BASE_URL = getBaseUrl();
+const AUTH_TOKEN = __ENV.API_TOKEN || 'test-token';
+
+const headers = {
+  'Content-Type': 'application/json',
+  'Authorization': `Bearer ${AUTH_TOKEN}`,
+};
+
+export default function () {
+  group('API Health', function () {
+    const res = http.get(`${BASE_URL}/health`, { headers });
+    checkResponse(res, 200);
+  });
+
+  group('Notifications', function () {
+    const payload = JSON.stringify({
+      userId: `user-${randomString()}`,
+      channel: 'email',
+      message: 'Load test notification',
+    });
+    const res = http.post(`${BASE_URL}/notifications`, payload, { headers });
+    checkResponse(res, 200);
+    notificationLatency.add(res.timings.duration);
+  });
+
+  group('Correlation', function () {
+    const res = http.get(`${BASE_URL}/correlation/events?limit=10`, { headers });
+    checkResponse(res, 200);
+    correlationLatency.add(res.timings.duration);
+  });
+}