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/registry/components/universal-form-modal/TableSectionRenderer.tsx

@@ -2132,6 +2132,101 @@ export function TableSectionRenderer({
     return Object.values(conditionalTableData).reduce((sum, data) => sum + data.length, 0);
   }, [conditionalTableData]);
 
+  // 조건부 테이블: 모달 중복 체크용 alreadySelected 구성
+  // DB에서 로드된 항목은 _sourceData가 없으므로 참조 ID 필드를 기반으로 _sourceData를 생성
+  const conditionalAlreadySelected = useMemo(() => {
+    const allItems = Object.values(conditionalTableData).flat();
+    if (allItems.length === 0) return allItems;
+
+    // 참조 ID 필드 탐색 (소스 테이블의 id를 저장하는 디테일 테이블 컬럼)
+    const referenceIdField = (tableConfig.columns || [])
+      .map((col) => col.saveConfig?.referenceDisplay?.referenceIdField)
+      .find(Boolean)
+      || (tableConfig.columns || [])
+        .map((col) => (col as any).dynamicSelectOptions?.rowSelectionMode?.targetIdField)
+        .find(Boolean);
+
+    // sourceField 매핑 수집 (소스 테이블 필드 → 디테일 테이블 필드)
+    const sourceFieldMap: Record<string, string> = {};
+    for (const col of tableConfig.columns || []) {
+      if (col.sourceField && col.sourceField !== col.field) {
+        sourceFieldMap[col.sourceField] = col.field;
+      }
+    }
+
+    return allItems.map((item) => {
+      if (item._sourceData) return item;
+
+      // DB에서 로드된 항목: _sourceData 재구성
+      const sourceData: any = {};
+
+      // 참조 ID 필드가 있으면 소스 테이블의 id로 매핑
+      if (referenceIdField && item[referenceIdField] !== undefined) {
+        sourceData.id = item[referenceIdField];
+      }
+
+      // sourceField 매핑을 역으로 적용 (디테일 필드 → 소스 필드)
+      for (const [srcField, detailField] of Object.entries(sourceFieldMap)) {
+        if (item[detailField] !== undefined) {
+          sourceData[srcField] = item[detailField];
+        }
+      }
+
+      // 디테일 테이블의 필드도 소스 데이터에 포함 (동일 필드명인 경우)
+      for (const col of tableConfig.columns || []) {
+        if (!col.sourceField && item[col.field] !== undefined) {
+          sourceData[col.field] = item[col.field];
+        }
+      }
+
+      return Object.keys(sourceData).length > 0
+        ? { ...item, _sourceData: sourceData }
+        : item;
+    });
+  }, [conditionalTableData, tableConfig.columns]);
+
+  // 일반 테이블: 모달 중복 체크용 alreadySelected 구성 (DB 로드 항목 대응)
+  const normalAlreadySelected = useMemo(() => {
+    if (tableData.length === 0) return tableData;
+
+    const referenceIdField = (tableConfig.columns || [])
+      .map((col) => col.saveConfig?.referenceDisplay?.referenceIdField)
+      .find(Boolean)
+      || (tableConfig.columns || [])
+        .map((col) => (col as any).dynamicSelectOptions?.rowSelectionMode?.targetIdField)
+        .find(Boolean);
+
+    const sourceFieldMap: Record<string, string> = {};
+    for (const col of tableConfig.columns || []) {
+      if (col.sourceField && col.sourceField !== col.field) {
+        sourceFieldMap[col.sourceField] = col.field;
+      }
+    }
+
+    return tableData.map((item) => {
+      if (item._sourceData) return item;
+
+      const sourceData: any = {};
+      if (referenceIdField && item[referenceIdField] !== undefined) {
+        sourceData.id = item[referenceIdField];
+      }
+      for (const [srcField, detailField] of Object.entries(sourceFieldMap)) {
+        if (item[detailField] !== undefined) {
+          sourceData[srcField] = item[detailField];
+        }
+      }
+      for (const col of tableConfig.columns || []) {
+        if (!col.sourceField && item[col.field] !== undefined) {
+          sourceData[col.field] = item[col.field];
+        }
+      }
+
+      return Object.keys(sourceData).length > 0
+        ? { ...item, _sourceData: sourceData }
+        : item;
+    });
+  }, [tableData, tableConfig.columns]);
+
   // ============================================
   // 조건부 테이블 렌더링
   // ============================================
@@ -2449,7 +2544,7 @@ export function TableSectionRenderer({
           multiSelect={multiSelect}
           filterCondition={conditionalFilterCondition}
           modalTitle={`${effectiveOptions.find((o) => o.value === modalCondition)?.label || modalCondition} - ${modalTitle}`}
-          alreadySelected={Object.values(conditionalTableData).flat()}
+          alreadySelected={conditionalAlreadySelected}
           uniqueField={tableConfig.saveConfig?.uniqueField}
           onSelect={handleConditionalAddItems}
           columnLabels={columnLabels}
@@ -2560,7 +2655,7 @@ export function TableSectionRenderer({
         multiSelect={multiSelect}
         filterCondition={baseFilterCondition}
         modalTitle={modalTitle}
-        alreadySelected={tableData}
+        alreadySelected={normalAlreadySelected}
         uniqueField={tableConfig.saveConfig?.uniqueField}
         onSelect={handleAddItems}
         columnLabels={columnLabels}