feat: Add savedIds to UPSERT response and update related components

- Enhanced the UPSERT process in DataService to include savedIds in the response, allowing tracking of newly saved record IDs.
- Updated the dataApi to reflect the new savedIds field in the Promise return type.
- Modified the SelectedItemsDetailInputComponent to handle and inject saved mapping IDs into detail records, improving data integrity and management during the save process.
- Added logging for savedIds to facilitate debugging and tracking of saved records.

frontend/lib/registry/components/selected-items-detail-input/SelectedItemsDetailInputComponent.tsx

@@ -689,6 +689,8 @@ export const SelectedItemsDetailInputComponent: React.FC<SelectedItemsDetailInpu
               // 레코드에 id(기존 DB PK)가 있으면 EDIT 모드 → 고아 삭제
               // id 없으면 CREATE 모드 → 기존 레코드 건드리지 않음
               const mappingHasDbIds = mappingRecords.some((r) => !!r.id);
+              // 저장된 매핑 ID를 추적 (디테일 테이블에 mapping_id 주입용)
+              let savedMappingIds: string[] = [];
               try {
                 const mappingResult = await dataApi.upsertGroupedRecords(
                   mainTable,
@@ -696,6 +698,11 @@ export const SelectedItemsDetailInputComponent: React.FC<SelectedItemsDetailInpu
                   mappingRecords,
                   { deleteOrphans: mappingHasDbIds },
                 );
+                // 백엔드에서 반환된 저장된 레코드 ID 목록
+                if (mappingResult.success && mappingResult.savedIds) {
+                  savedMappingIds = mappingResult.savedIds;
+                  console.log(`✅ ${mainTable} 저장 완료, savedIds:`, savedMappingIds);
+                }
               } catch (err) {
                 console.error(`❌ ${mainTable} 저장 실패:`, err);
               }
@@ -755,6 +762,18 @@ export const SelectedItemsDetailInputComponent: React.FC<SelectedItemsDetailInpu
                   priceRecords.push(emptyRecord);
                 }
 
+                // Step1에서 저장된 매핑 ID를 디테일 레코드에 주입
+                // (customer_item_prices.mapping_id ← customer_item_mapping.id)
+                if (savedMappingIds.length > 0) {
+                  const mappingId = savedMappingIds[0]; // 일반적으로 1:N (매핑 1개 : 단가 N개)
+                  priceRecords.forEach((record) => {
+                    if (!record.mapping_id) {
+                      record.mapping_id = mappingId;
+                    }
+                  });
+                  console.log(`🔗 디테일 레코드에 mapping_id 주입: ${mappingId}`);
+                }
+
                 const priceHasDbIds = priceRecords.some((r) => !!r.id);
                 try {
                   const detailResult = await dataApi.upsertGroupedRecords(