refactor: replace Spring Boot with Jooby framework

- Remove Spring Boot dependencies and annotations.
- Implement Jooby MVC controllers and Guice dependency injection.
- Migrate persistence layer to Ebean ORM.
- Configure Flyway migrations and ApiErrorController.
- Update application configuration to HOCON format.

.env.example

@@ -1,5 +1,3 @@
-SPRING_PROFILES_ACTIVE=dev
-
 APP_ALLOWED_ORIGINS='http://127.0.0.1:3000, http://localhost:3000'
 
 DB_NAME=EXAMPLE_DB