Add build and Lighthouse performance tests for React admin template

[devin-ai-integration]

Summary

This PR adds performance testing infrastructure for the CoreUI React Admin Template, including:

• GitHub Actions workflow (performance-tests.yml) that runs on push/PR to main and can be triggered manually
• Build performance test script (build-perf-test.js) that measures:
  • Build time (threshold: 2 minutes)
  • Total bundle size (threshold: 5MB)
  • Chunk count (threshold: 50 chunks)
  • Largest chunk size (threshold: 2MB)
  • Lint execution time (threshold: 30 seconds)
• Lighthouse CI configuration (lighthouserc.json) with thresholds for Core Web Vitals and accessibility scores

The workflow uploads test results as artifacts and runs Lighthouse audits against the built static files.

Review & Testing Checklist for Human

• Verify build output directory: The script assumes ./build as the output directory - confirm this matches Vite's build.outDir configuration in vite.config.mjs
• Validate thresholds are appropriate: The hardcoded thresholds (2 min build, 5MB bundle, 50 chunks) are estimates - run node tests/performance/build-perf-test.js locally to see actual values and adjust if needed
• Review Lighthouse continue-on-error: true: This means Lighthouse failures won't block the workflow - confirm this is intentional behavior
• Test the workflow end-to-end: Trigger the workflow manually via GitHub Actions to verify it completes successfully

Recommended Test Plan

1. Run npm ci && node tests/performance/build-perf-test.js locally to verify the script works
2. Check the generated tests/performance/results.json for reasonable values
3. After merging, trigger the workflow manually and verify both jobs complete

Notes

• The lint test marks as "passed" even with warnings/errors (only measures time) - this may need adjustment based on team preferences
• Lighthouse results are uploaded to temporary public storage for viewing

Link to Devin run: https://partner-workshops.devinenterprise.com/sessions/cf94d817dd244336971fd9b8333d75d7

[devin-ai-integration]

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