feat(benchmarks): add JMH benchmarks for performance testing and load scripts

load-tests/README.md

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+# NowChess Load Testing with k6
+
+Performance testing suite for NowChess services using k6.
+
+## Installation
+
+```bash
+# Install k6 (macOS)
+brew install k6
+
+# Or download from https://k6.io/docs/getting-started/installation/
+```
+
+## Test Scenarios
+
+### 1. Ramp-Up Test
+Gradually increases load from 10 to 100 concurrent users.
+
+```bash
+k6 run ramp-up.js
+```
+
+Target: Identify system behavior under gradual load increase.
+
+### 2. Stress Test
+Incremental load increase up to 500 concurrent users to find breaking point.
+
+```bash
+k6 run stress-test.js
+```
+
+Target: Determine system capacity and failure point.
+
+### 3. Spike Test
+Sudden traffic surge (baseline 50 → 500 users instantly).
+
+```bash
+k6 run spike-test.js
+```
+
+Target: Test recovery and resilience to sudden spikes.
+
+### 4. Constant Load Test
+Maintains 50 VUs for 10 minutes.
+
+```bash
+k6 run constant-load.js
+```
+
+Target: Check stability under sustained load.
+
+## Environment Variables
+
+```bash
+# Override service endpoints
+export BASE_URL=http://localhost:8080
+export ACCOUNT_HOST=http://localhost:8083
+export STORE_HOST=http://localhost:8085
+
+k6 run ramp-up.js
+```
+
+## Prerequisites
+
+Ensure services are running:
+- Core: `localhost:8080`
+- Account: `localhost:8083`
+- Store: `localhost:8085`
+- Redis: `localhost:6379` (with increased pool size)
+
+## Metrics Interpretation
+
+- `http_req_duration`: Response time (p95, p99 percentiles matter most)
+- `http_req_failed`: Failed requests (connection errors, errors, non-2xx responses)
+- `vus`: Virtual Users (concurrent connections)
+- `iterations`: Completed test cycles per VU
+
+## Results
+
+k6 generates HTML report output. Use with:
+
+```bash
+k6 run --out=csv=results.csv ramp-up.js
+```
+
+## Troubleshooting
+
+If you see:
+- **"max pool wait timeout"** → Redis pool still too small or maxWaitTime too short
+- **"connection refused"** → Service not running
+- **"high p99 latency"** → System approaching capacity
+
+Increase Redis pool settings in `modules/*/src/main/resources/application.yml`:
+```yaml
+quarkus:
+  redis:
+    pool:
+      max-size: 128  # Increase if still hitting limits
+      max-waiting: 256
+```