fix(select): Radix UI Select v2.x value="" 에러 수정

Radix UI Select v2.0부터 빈 문자열 value=""가 금지됨 (placeholder 예약어)

수정 파일:
- FieldDetailSettingsModal.tsx: saveColumn "__default__"
- TableLogViewer.tsx: 전체 필터 "__all__"
- FlowStepPanel.tsx: disabled placeholder "__placeholder__"
- MapConfigPanel.tsx: 선택 안 함 "__none__" (2곳)
- DataMappingSettings.tsx: disabled placeholder "__placeholder__" (2곳)
- ScreenAssignmentTab.tsx: disabled placeholder "__placeholder__"
- multilang/page.tsx: 전체 메뉴/타입 "__all__" (2곳)

frontend/components/dataflow/external-call/DataMappingSettings.tsx

@@ -236,12 +236,13 @@ export const DataMappingSettings: React.FC<DataMappingSettingsProps> = ({
                         <SelectValue placeholder={tablesLoading ? "테이블 목록 로딩 중..." : "저장할 테이블을 선택하세요"} />
                       </SelectTrigger>
                       <SelectContent>
+                        {/* Radix UI Select v2.x: 빈 문자열 value="" 금지 → "__placeholder__" 사용 */}
                         {tablesLoading ? (
-                          <SelectItem value="" disabled>
+                          <SelectItem value="__placeholder__" disabled>
                             테이블 목록 로딩 중...
                           </SelectItem>
                         ) : availableTables.length === 0 ? (
-                          <SelectItem value="" disabled>
+                          <SelectItem value="__placeholder__" disabled>
                             사용 가능한 테이블이 없습니다
                           </SelectItem>
                         ) : (