Add k6 load test scripts for Darkwatch authentication endpoints (FRE-4928)

- darkwatch-auth.js: k6 script testing POST /auth/login, /auth/logout, /auth/refresh
- P99 thresholds: login <200ms, logout <100ms, refresh <150ms
- Config: 500 req/s sustained for 5 minutes
- Mixed workload scenario + individual endpoint scenarios
- .env.example and run.sh for execution
Co-Authored-By: Paperclip <noreply@paperclip.ing>

load-tests/darkwatch-auth/.env.example

@@ -0,0 +1,20 @@
+# Darkwatch Auth Load Test Configuration
+# Copy to .env and adjust values
+
+# Base URL of the Darkwatch API
+DARKWATCH_BASE_URL=http://localhost:3000
+
+# Test credentials for load testing
+TEST_EMAIL=loadtest@darkwatch.shieldai
+TEST_PASSWORD=LoadTest2026!
+
+# Test duration (default: 300s = 5 minutes)
+DURATION=300s
+
+# Target requests per second (default: 500)
+TARGET_RPS=500
+
+# P99 latency thresholds in milliseconds
+LOGIN_P99_MS=200
+LOGOUT_P99_MS=100
+REFRESH_P99_MS=150