feat: add configuration files and scripts for project setup ✨

🚀 Breaking Changes:
- Introduced new environment variables for GitLab API integration
- Added validation script for PR checks
- Updated package.json with new scripts for testing and formatting

📝 Details:
- Added .prettierrc and .eslintrc.json for code formatting and linting
- Created .env.example for environment variable setup
- Updated CHANGELOG.md with recent changes
- Added documentation for GitHub secrets setup

.github/pr-validation-guide.md

@@ -0,0 +1,96 @@
+# PR Validation Guide
+
+## Overview
+
+All Pull Requests are now automatically tested and validated. Manual testing is no longer required!
+
+## Automated Validation Items
+
+### 1. Build and Type Check
+
+- TypeScript compilation success
+- No type errors
+
+### 2. Testing
+
+- **Unit Tests**: API endpoints, error handling, authentication, etc.
+- **Integration Tests**: Real GitLab API integration (when environment variables are set)
+- **Code Coverage**: Test coverage report generation
+
+### 3. Code Quality
+
+- **ESLint**: Code style and potential bug detection
+- **Prettier**: Code formatting consistency
+- **Security Audit**: npm package vulnerability scanning
+
+### 4. Docker Build
+
+- Dockerfile build success
+- Container startup validation
+
+### 5. Node.js Version Compatibility
+
+- Tested across Node.js 18.x, 20.x, and 22.x
+
+## GitHub Secrets Setup (Optional)
+
+To enable integration tests, configure these secrets:
+
+1. `GITLAB_TOKEN_TEST`: GitLab Personal Access Token
+2. `TEST_PROJECT_ID`: Test GitLab project ID
+3. `GITLAB_API_URL`: GitLab API URL (default: https://gitlab.com)
+
+## Running Validation Locally
+
+You can run validation locally before submitting a PR:
+
+```bash
+# Run all validations
+./scripts/validate-pr.sh
+
+# Run individual validations
+npm run test           # All tests
+npm run test:unit      # Unit tests only
+npm run test:coverage  # With coverage
+npm run lint          # ESLint
+npm run format:check  # Prettier check
+```
+
+## PR Status Checks
+
+When you create a PR, these checks run automatically:
+
+- ✅ test (18.x)
+- ✅ test (20.x)
+- ✅ test (22.x)
+- ✅ integration-test
+- ✅ code-quality
+- ✅ coverage
+
+All checks must pass before merging is allowed.
+
+## Troubleshooting
+
+### Test Failures
+
+1. Check the failed test in the PR's "Checks" tab
+2. Review specific error messages in the logs
+3. Run the test locally to debug
+
+### Formatting Errors
+
+```bash
+npm run format      # Auto-fix formatting
+npm run lint:fix    # Auto-fix ESLint issues
+```
+
+### Type Errors
+
+```bash
+npx tsc --noEmit    # Run type check only
+```
+
+## Dependabot Auto-merge
+
+- Minor and patch updates are automatically merged
+- Major updates require manual review