feat: add reports mechanism
- Add Report entity with project, student, report_text, report_type, timestamps and review fields
- Add ReportRepository with methods to find reports by project, student, review status
- Add DTOs: ReportRequestDTO, ReportResponseDTO, ReviewReportDTO
- Add ReportService with create, update, review and get reports functionality
- Add ReportController with 8 REST API endpoints
- Add SQL migration for reports table with indexes
- Add API documentation (REPORTS_API_DOCUMENTATION.md)
Report types: INTERMEDIATE, FINAL Report statuses: PENDING_REVIEW, REVIEWED