테이블 컬럼 중복 삽입 안되게 수정

frontend/components/screen/panels/ComponentsPanel.tsx

@@ -18,6 +18,7 @@ interface ComponentsPanelProps {
   onSearchChange?: (value: string) => void;
   onTableDragStart?: (e: React.DragEvent, table: TableInfo, column?: ColumnInfo) => void;
   selectedTableName?: string;
+  placedColumns?: Set<string>; // 이미 배치된 컬럼명 집합
 }
 
 export function ComponentsPanel({ 
@@ -26,7 +27,8 @@ export function ComponentsPanel({
   searchTerm = "", 
   onSearchChange, 
   onTableDragStart,
-  selectedTableName 
+  selectedTableName,
+  placedColumns 
 }: ComponentsPanelProps) {
   const [searchQuery, setSearchQuery] = useState("");
 
@@ -207,6 +209,7 @@ export function ComponentsPanel({
               onSearchChange={onSearchChange || (() => {})}
               onDragStart={onTableDragStart}
               selectedTableName={selectedTableName}
+              placedColumns={placedColumns}
             />
           ) : (
             <div className="flex h-32 items-center justify-center text-center">