Refactor load testing scripts to support Bash and PowerShell

- Updated README.md to reflect changes in load testing commands and added usage examples for Bash scripts.
- Converted PowerShell load testing scripts to Bash equivalents for better cross-platform compatibility.
- Added new Bash scripts: run-loadtests.sh, summarize-artillery.sh, and summarize-k6.sh to mirror existing PowerShell functionality.
- Updated admin-api.js and ws-chat.yml for consistency and improved performance metrics reporting.
- Enhanced error handling and output formatting in summary scripts for better readability.

scripts/loadtest/summarize-k6.sh

@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+# summarize-k6.sh — Extract per-endpoint p95 and failure rates from a k6 JSON
+# summary export. Mirrors scripts/loadtest/summarize-k6.ps1.
+# Usage: ./scripts/loadtest/summarize-k6.sh <k6-summary.json>
+set -euo pipefail
+
+if [[ $# -lt 1 ]]; then
+  echo "Usage: $0 <k6-summary.json>" >&2
+  exit 2
+fi
+summary_file="$1"
+[[ -f "$summary_file" ]] || { echo "Summary file not found: $summary_file" >&2; exit 1; }
+
+SUMMARY_FILE="$summary_file" node <<'EOF'
+const fs = require('fs');
+const summary = JSON.parse(fs.readFileSync(process.env.SUMMARY_FILE, 'utf8'));
+const metrics = summary.metrics;
+if (!metrics) throw new Error('Invalid k6 summary file: missing metrics object.');
+
+const val = (m, key) => (m && m.values && m.values[key] !== undefined) ? Number(m.values[key]) : undefined;
+const globalDuration = val(metrics.http_req_duration, 'p(95)');
+const globalFailRate = val(metrics.http_req_failed, 'rate');
+
+console.log(`k6 Summary: ${process.env.SUMMARY_FILE}`);
+if (globalDuration !== undefined) console.log(`Global p95 duration (ms): ${globalDuration.toFixed(2)}`);
+if (globalFailRate !== undefined) console.log(`Global failure rate: ${(globalFailRate * 100).toFixed(2)}%`);
+console.log('');
+
+const endpoints = ['overview', 'analytics', 'chat_log', 'users'];
+const rows = endpoints.map((ep) => {
+  const dP95 = val(metrics[`http_req_duration{endpoint:${ep}}`], 'p(95)');
+  const fRate = val(metrics[`http_req_failed{endpoint:${ep}}`], 'rate');
+  return {
+    Endpoint: ep,
+    P95Ms: dP95 !== undefined ? dP95.toFixed(2) : 'n/a',
+    FailurePct: fRate !== undefined ? (fRate * 100).toFixed(4) : 'n/a',
+  };
+});
+
+const pad = (s, n) => String(s).padEnd(n);
+console.log(pad('ENDPOINT', 12) + pad('P95_MS', 10) + 'FAILURE_PCT');
+for (const r of rows) console.log(pad(r.Endpoint, 12) + pad(r.P95Ms, 10) + r.FailurePct);
+EOF