Add backend test suite + GitHub Actions CI pipeline

[BhaveshBytess]

Description

Hi maintainers! 👋

I would like to contribute by adding an initial backend test setup and GitHub Actions CI pipeline.

Proposed Work

1. Introduce test framework (Vitest or Jest) in apps/api

   • Configure test environment
   • Add pnpm test script
   • Provide a minimal folder structure: /apps/api/tests

2. Add first unit tests

   • Target services/project.service.ts
   • Specifically test:
     • GitHub query generation
     • Filter params (languages, stars, forks)
     • Handling GitHub API errors / edge cases

3. Add GitHub Actions workflow

   • Install dependencies (pnpm)
   • Run ESLint
   • Run TypeScript type check
   • Run the new test suite

4. Documentation

   • Update CONTRIBUTING.md with testing + CI instructions

Why this is useful

• The repo currently has no test suite or CI checks.
• Adding both increases reliability and safety for future PRs.
• Tests for GitHub project fetching ensure backend correctness.

Please let me know if I can proceed and whether you prefer Jest or Vitest.
Happy to adjust the plan! 🚀

Context

No response

Additional Information

No response