feat: nullable projectId, new ticket categories, improved create form

backend/src/main/java/com/srsystem/service/TicketService.java

@@ -59,21 +59,22 @@ public class TicketService {
         Employee requester = employeeRepository.findById(requesterId)
                 .orElseThrow(() -> new BusinessException(ErrorCode.EMPLOYEE_NOT_FOUND));
         
-        Project project = projectRepository.findById(request.projectId())
-                .orElseThrow(() -> new BusinessException(ErrorCode.PROJECT_NOT_FOUND));
-
-        Ticket ticket = Ticket.builder()
-                .project(project)
+        Ticket.TicketBuilder builder = Ticket.builder()
                 .requester(requester)
                 .category(request.category())
                 .priority(request.priority())
                 .title(request.title())
                 .description(request.description())
                 .status(TicketStatus.OPEN)
-                .slaWarnFlag('N')
-                .build();
+                .slaWarnFlag('N');
 
-        Ticket saved = ticketRepository.save(ticket);
+        if (request.projectId() != null) {
+            Project project = projectRepository.findById(request.projectId())
+                    .orElseThrow(() -> new BusinessException(ErrorCode.PROJECT_NOT_FOUND));
+            builder.project(project);
+        }
+
+        Ticket saved = ticketRepository.save(builder.build());
         return toIssueTicket(saved);
     }