feat: Implement entity join functionality in V2Repeater and configuration panel

- Added support for entity joins in the V2Repeater component, allowing for automatic resolution of foreign key references to display data from related tables.
- Introduced a new `resolveEntityJoins` function to handle the fetching and mapping of reference data based on configured entity joins.
- Enhanced the V2RepeaterConfigPanel to manage entity join configurations, including loading available columns and toggling join settings.
- Updated the data handling logic to incorporate mapping rules for incoming data, ensuring that only necessary fields are retained during processing.
- Improved user experience by providing clear logging and feedback during entity join resolution and data mapping operations.

frontend/lib/utils/buttonActions.ts

@@ -2339,9 +2339,12 @@ export class ButtonActionExecutor {
     }
 
     // 🎯 채번 규칙 할당 처리 (저장 시점에 실제 순번 증가)
-    // 🔧 수정 모드 체크: formData.id 또는 originalGroupedData가 있으면 UPDATE 모드
+    // 🔧 수정 모드 체크: _mainRecordId, formData.id 또는 originalGroupedData가 있으면 UPDATE 모드
+    const parentMainRecordId = modalData._mainRecordId || formData._mainRecordId;
     const isEditModeUniversal =
-      (formData.id !== undefined && formData.id !== null && formData.id !== "") || originalGroupedData.length > 0;
+      (parentMainRecordId !== undefined && parentMainRecordId !== null && parentMainRecordId !== "") ||
+      (formData.id !== undefined && formData.id !== null && formData.id !== "") ||
+      originalGroupedData.length > 0;
 
     const fieldsWithNumbering: Record<string, string> = {};
 
@@ -2417,6 +2420,13 @@ export class ButtonActionExecutor {
       );
 
       if (hasSeparateTargetTable && Object.keys(commonFieldsData).length > 0) {
+        // _mainRecordId: 분할패널에서 전달한 실제 메인 레코드 ID (formData.id는 디테일 레코드 ID일 수 있음)
+        const mainRecordIdFromParent =
+          modalData._mainRecordId || formData._mainRecordId || commonFieldsData._mainRecordId;
+        // 메인 테이블 ID 결정: _mainRecordId > formData.id 순서로 탐색
+        const existingMainId = mainRecordIdFromParent || formData.id;
+        const isMainUpdate = existingMainId !== undefined && existingMainId !== null && existingMainId !== "";
+
         const mainRowToSave = { ...commonFieldsData, ...userInfo };
 
         // 메타데이터 제거
@@ -2426,24 +2436,15 @@ export class ButtonActionExecutor {
           }
         });
 
-        // 🆕 메인 테이블 UPDATE/INSERT 판단
-        // - formData.id가 있으면 편집 모드 → UPDATE
-        // - formData.id가 없으면 신규 등록 → INSERT
-        const existingMainId = formData.id;
-        const isMainUpdate = existingMainId !== undefined && existingMainId !== null && existingMainId !== "";
-
         let mainSaveResult: { success: boolean; data?: any; message?: string };
 
         if (isMainUpdate) {
-          // 🔄 편집 모드: UPDATE 실행
-
           mainSaveResult = await DynamicFormApi.updateFormData(existingMainId, {
             tableName: tableName!,
             data: mainRowToSave,
           });
           mainRecordId = existingMainId;
         } else {
-          // ➕ 신규 등록: INSERT 실행
           console.log("➕ [handleUniversalFormModalTableSectionSave] 메인 테이블 INSERT 실행");
           mainSaveResult = await DynamicFormApi.saveFormData({
             screenId: screenId!,
@@ -2471,8 +2472,32 @@ export class ButtonActionExecutor {
 
         // 1️⃣ 신규 품목 INSERT (id가 없는 항목)
         const newItems = currentItems.filter((item) => !item.id);
+        const existingItemsForRef = currentItems.filter((item) => item.id);
+
+        // 기존 DB 항목에서 공통 필드 추출 (수정 모달에서 commonFieldsData에 누락된 필드 보완)
+        // 예: item_code, item_name 등이 commonFieldsData에 없으면 기존 항목에서 가져옴
+        const sharedFieldsFromExisting: Record<string, any> = {};
+        if (existingItemsForRef.length > 0 && newItems.length > 0) {
+          const refItem = existingItemsForRef[0];
+          for (const [key, val] of Object.entries(refItem)) {
+            if (
+              key !== "id" &&
+              !key.startsWith("_") &&
+              val !== undefined &&
+              val !== null &&
+              val !== "" &&
+              commonFieldsData[key] === undefined
+            ) {
+              sharedFieldsFromExisting[key] = val;
+            }
+          }
+          if (Object.keys(sharedFieldsFromExisting).length > 0) {
+            console.log("📋 [INSERT] 기존 항목에서 공통 필드 보완:", Object.keys(sharedFieldsFromExisting));
+          }
+        }
+
         for (const item of newItems) {
-          const rowToSave = { ...commonFieldsData, ...item, ...userInfo };
+          const rowToSave = { ...sharedFieldsFromExisting, ...commonFieldsData, ...item, ...userInfo };
 
           Object.keys(rowToSave).forEach((key) => {
             if (key.startsWith("_")) {
@@ -6484,6 +6509,12 @@ export class ButtonActionExecutor {
         return true;
       } else {
         // 기본: 분할 패널 데이터 전달 이벤트
+        console.log("📤 [transferData] splitPanelDataTransfer 발송:", {
+          rowCount: selectedRows.length,
+          mappingRules,
+          sampleRow: selectedRows[0],
+          hasItemId: selectedRows[0]?.item_id,
+        });
 
         const transferEvent = new CustomEvent("splitPanelDataTransfer", {
           detail: {