feat: add health, stats, OpenAPI, security headers, tests

- /api/health — uptime, version, memory usage
- /api/stats — request count, error rate, cache info
- /api/openapi — OpenAPI 3.0.3 specification
- Security headers: X-Frame-Options, X-Content-Type-Options, X-XSS-Protection
- Request counter middleware
- CONTRIBUTING.md — contribution guidelines
- test.js — integration test suite (18 endpoints)

CONTRIBUTING.md

@@ -0,0 +1,84 @@
+# Contributing to AniKotoAPI
+
+Thank you for your interest in contributing! Here's how you can help.
+
+## Getting Started
+
+1. Fork the repository
+2. Clone your fork: `git clone https://github.com/YOUR_USERNAME/AniKotoAPI.git`
+3. Create a branch: `git checkout -b feature/amazing-feature`
+4. Make your changes
+5. Commit: `git commit -m 'feat: add amazing feature'`
+6. Push: `git push origin feature/amazing-feature`
+7. Open a Pull Request
+
+## Development Setup
+
+```bash
+# Install dependencies
+npm install
+
+# Start development server
+npm run dev
+
+# Server runs on http://localhost:4444
+```
+
+## Project Structure
+
+```
+AniKotoAPI/
+├── server.js              # Express entry point
+├── src/
+│   ├── configs/           # URL patterns, headers, ID mappings
+│   ├── controllers/       # Route handlers
+│   ├── extractors/        # HTML scrapers (Cheerio)
+│   ├── helper/            # Cache utilities
+│   └── routes/            # Express routes
+├── public/                # Static files (landing page)
+└── docs/                  # API documentation
+```
+
+## Adding a New Endpoint
+
+1. Create extractor in `src/extractors/yourExtractor.js`
+2. Create controller in `src/controllers/yourController.js`
+3. Add route in `src/routes/apiRoutes.js`
+4. Update `docs/endpoints.md` with documentation
+5. Test with `curl http://localhost:4444/api/your-endpoint`
+
+## Code Style
+
+- Use ES6+ features (import/export, async/await)
+- Add JSDoc comments for new functions
+- Follow existing patterns in the codebase
+- Keep extractors focused on one task
+
+## Commit Messages
+
+Use [Conventional Commits](https://www.conventionalcommits.org/):
+
+- `feat:` new feature
+- `fix:` bug fix
+- `docs:` documentation changes
+- `refactor:` code refactoring
+- `test:` adding tests
+- `chore:` maintenance
+
+## Pull Request Guidelines
+
+- Keep PRs focused on one feature or fix
+- Update CHANGELOG.md with your changes
+- Test your changes locally before submitting
+- Follow existing code style
+
+## Reporting Issues
+
+- Use GitHub Issues for bug reports
+- Include steps to reproduce
+- Include expected vs actual behavior
+- Include your Node.js version
+
+## License
+
+By contributing, you agree that your contributions will be licensed under the MIT License.