عرض عملي: استبدال المستودع في الذاكرة بـ Spring JDBC

خطوة بخطوة

1. Show the existing ProductRepository interface and the in-memory implementation.
2. Apply schema.sql manually in local PostgreSQL and add the datasource properties.
3. Create JdbcProductRepository implements ProductRepository using JdbcClient and a shared mapper.
4. Planned mistake: forget the @Repository/bean switch so two implementations exist; show the startup error and remove the in-memory bean.
5. Run the existing API tests; they pass unchanged.
6. Add one integration test against a real PostgreSQL database.