feat: Add Codecov integration to CI workflow

[fedosov]

Summary

Integrates Codecov coverage reporting into the existing GitHub Actions CI workflow. This enables automated code coverage tracking and reporting on pull requests.

Changes

• Updated .github/workflows/ci.yml: Added Codecov upload step using codecov/codecov-action@v5 after test execution
• Created codecov.yml: Configuration file with:
  • Informational coverage tracking (no failure thresholds)
  • 2 decimal precision for coverage percentages
  • Automatic PR comments with coverage diff
  • Test file exclusions from coverage calculations

Configuration Details

• Uses global upload token via CODECOV_TOKEN GitHub secret
• Uploads coverage-final.json generated by Jest
• Set fail_ci_if_error: false to prevent CI failures on Codecov upload issues
• Flags coverage as unittests for organization

Manual Setup Required

Action needed: Add CODECOV_TOKEN secret to repository:

1. Generate global upload token in Codecov dashboard (requires org admin)
2. Go to Repository Settings → Secrets and variables → Actions
3. Add secret named CODECOV_TOKEN with token value

Test Results

All existing tests pass (9 test suites, 122 tests):

• ✅ data-normalizer.test.js
• ✅ decimal-converter.test.js
• ✅ error-parser.test.js
• ✅ event-parser.test.js
• ✅ network-switcher.test.js
• ✅ bridge-filter.test.js
• ✅ settings-consistency.test.js
• ✅ fetch-last-transfers.test.js
• ✅ retry-with-fallback.test.js

🤖 Generated with Claude Code

[codecov]

Welcome to Codecov 🎉

Once you merge this PR into your default branch, you're all set! Codecov will compare coverage reports and display results in all future pull requests.

Thanks for integrating Codecov - We've got you covered ☂️