[DevOps/CI] Automated Code Coverage Enforcement & Vitest CI Gate

[blurbeast]

Overview & Background

To maintain high code quality across the codebase as open-source contributors submit pull requests, an automated test coverage enforcement gate is required in GitHub Actions CI to prevent coverage regressions.

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Technical Specification & Architecture

1. Vitest Coverage Configuration:
   • Configure @vitest/coverage-v8 in backend/vitest.config.ts and frontend/vitest.config.ts.
   • Set minimum coverage thresholds:
     • Statements: 80%
     • Branches: 75%
     • Functions: 80%
     • Lines: 80%
2. GitHub Actions Integration:
   • Add coverage generation step in .github/workflows/ci.yml.
   • Post automated coverage summary comment on pull requests.
   • Fail PR build if coverage decreases by $> 1%$.

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Target Files

• backend/vitest.config.ts
• frontend/vitest.config.ts
• .github/workflows/ci.yml
• .github/codecov.yml

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Acceptance Criteria

• Vitest generates lcov coverage reports for backend and frontend.
• CI workflow fails if code coverage falls below threshold.
• Automated PR summary table showing coverage changes per modified file.

[jchinedu]

let me work on this issue