refactor(resolvers): update resolvers to use full entities
- Update EmploymentResolver to fetch full entities before creating/updating
- Inject CompanyService, RoleService, LevelService, SkillService for entity fetching
- Update UserFieldResolver to use findForUser method
- Remove user field from UserJobExperience GraphQL type
- Update fromDomain static method to handle new entity structure
- Implement proper domain-driven design in GraphQL layer