fix: Enhance error handling and validation messages in form data operations

- Integrated `formatPgError` utility to provide user-friendly error messages based on PostgreSQL error codes during form data operations.
- Updated error responses in `saveFormData`, `saveFormDataEnhanced`, `updateFormData`, and `updateFormDataPartial` to include specific messages based on the company context.
- Improved error handling in the frontend components to display relevant error messages from the server response, ensuring users receive clear feedback on save operations.
- Enhanced the required field validation by incorporating NOT NULL metadata checks across various components, improving the accuracy of form submissions.

These changes improve the overall user experience by providing clearer error messages and ensuring that required fields are properly validated based on both manual settings and database constraints.

backend-node/src/middleware/errorHandler.ts

@@ -47,7 +47,10 @@ export const errorHandler = (
       error = new AppError("참조 무결성 제약 조건 위반입니다.", 400);
     } else if (pgError.code === "23502") {
       // not_null_violation
-      error = new AppError("필수 입력값이 누락되었습니다.", 400);
+      const colName = pgError.column || "";
+      const tableName = pgError.table || "";
+      const detail = colName ? ` [${tableName}.${colName}]` : "";
+      error = new AppError(`필수 입력값이 누락되었습니다.${detail}`, 400);
     } else if (pgError.code.startsWith("23")) {
       // 기타 무결성 제약 조건 위반
       error = new AppError("데이터 무결성 제약 조건 위반입니다.", 400);
@@ -84,6 +87,7 @@ export const errorHandler = (
   // 응답 전송
   res.status(statusCode).json({
     success: false,
+    message: message,
     error: {
       message: message,
       ...(process.env.NODE_ENV === "development" && { stack: error.stack }),