Add news API integration and related configurations

- Update .env.example to include NEWS_API_KEY configuration
- Add newsapi-python dependency in pyproject.toml
- Implement NewsAPI class for fetching news articles
- Create Article model for structured news data
- Add tests for NewsAPI functionality in test_news_api.py
- Update pytest configuration to include news marker

pyproject.toml

@@ -31,6 +31,9 @@ dependencies = [
     # ✅ per interagire con API di exchange di criptovalute
     "coinbase-advanced-py",
     "python-binance",
+
+    # ✅ per interagire con API di notizie
+    "newsapi-python",
 ]
 
 [tool.pytest.ini_options]