refactor: Enhance unique constraint validation across data operations

- Integrated `TableManagementService` to validate unique constraints before insert, update, and upsert actions in various controllers, including `dataflowExecutionController`, `dynamicFormController`, and `tableManagementController`.
- Improved error handling in `errorHandler` to provide detailed messages indicating which field has a unique constraint violation.
- Updated the `formatPgError` utility to extract and display specific column labels for unique constraint violations, enhancing user feedback.
- Adjusted the table schema retrieval to include company-specific nullable and unique constraints, ensuring accurate representation of database rules.

These changes improve data integrity by preventing duplicate entries and enhance user experience through clearer error messages related to unique constraints.

backend-node/src/controllers/tableManagementController.ts

@@ -2087,6 +2087,23 @@ export async function multiTableSave(
       return;
     }
 
+    // UNIQUE 제약조건 검증 (트랜잭션 전에)
+    const tmsMulti = new TableManagementService();
+    const uniqueViolations = await tmsMulti.validateUniqueConstraints(
+      mainTable.tableName,
+      mainData,
+      companyCode,
+      isUpdate ? mainData[mainTable.primaryKeyColumn] : undefined
+    );
+    if (uniqueViolations.length > 0) {
+      client.release();
+      res.status(400).json({
+        success: false,
+        message: `중복된 값이 존재합니다: ${uniqueViolations.join(", ")}`,
+      });
+      return;
+    }
+
     await client.query("BEGIN");
 
     // 1. 메인 테이블 저장