Updated target framework to .NET 9 across multiple projects and updated package references. Refactored `HospitalController` to use MediatR commands. Introduced new patient-related functionalities including new API endpoints, commands, queries, and DTOs. Removed user-related properties from medical history mappings. Added new handlers for patient creation, retrieval, and section updates.
- Updated MedicalHistoryController to use MediatR for commands/queries
- Refactored methods in MedicalHistoryController to use expression-bodied members
- Added HospitalId property to CurrentUserService
- Removed UniversityId claims handling from JwtService
- Updated AccountService to handle Student entities with UniversityId and SectionId
- Removed IMedicalHistoryService interface and its implementation
- Removed UniversityId and SectionId handling from UserService
- Added SectionId property to SignUpRequestDto
- Refactored MedicalHistory entity to remove personal information properties
- Added CreateMedicalHistoryCommand, UpdateMedicalHistoryCommand, and DeleteMedicalHistoryCommand
- Added command handlers for medical history commands
