Upgrade App to Latest JDK and Spring Boot

I need an experienced Java developer to upgrade my app to the latest JDK and Spring Boot version. The current JDK version of my app is JDK 8 and the Spring Boot version is 4.0. There are no additional features or enhancements required, just the upgrade.

Please ensure you have:
- Extensive experience with Java and Spring Boot
- Previous project experience involving similar upgrades
- Ability to deliver high-quality work within the deadline