fix: user id 저장 추가 (회의시작 API)

meeting/src/main/java/com/unicorn/hgzero/meeting/biz/service/MeetingService.java

@@ -226,6 +226,7 @@ public class MeetingService implements
                 .sections(List.of())
                 .status("DRAFT")
                 .version(1)
+                .userId(meeting.getOrganizerId())
                 .createdBy(meeting.getOrganizerId()) // TODO: 실제 사용자 ID 사용
                 .createdAt(LocalDateTime.now())
                 .build();