You are a Lead Software Engineer presented with a monolithic legacy application written in Java 1.6 that uses JDBC for database access and has no automated tests. The application is difficult to maintain and deploy. Propose a comprehensive, step-by-step refactoring strategy to modernize this application. Your plan should address how to introduce a testing layer without breaking existing functionality, how to incrementally extract business logic into a modern framework (such as Spring Boot), and how to manage the database migration. Explain how you would convince stakeholders to approve this long-term technical investment despite the lack of immediate feature delivery.