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/utils/pgErrorUtil.ts

@@ -0,0 +1,50 @@
+import { query } from "../database/db";
+
+/**
+ * PostgreSQL 에러를 사용자 친절한 메시지로 변환
+ * table_type_columns의 column_label을 조회하여 한글 라벨로 표시
+ */
+export async function formatPgError(
+  error: any,
+  companyCode?: string
+): Promise<string> {
+  if (!error || !error.code) {
+    return error?.message || "데이터 처리 중 오류가 발생했습니다.";
+  }
+
+  switch (error.code) {
+    case "23502": {
+      // not_null_violation
+      const colName = error.column || "";
+      const tblName = error.table || "";
+
+      if (colName && tblName && companyCode) {
+        try {
+          const rows = await query(
+            `SELECT column_label FROM table_type_columns 
+             WHERE table_name = $1 AND column_name = $2 AND company_code = $3 
+             LIMIT 1`,
+            [tblName, colName, companyCode]
+          );
+          const label = rows[0]?.column_label;
+          if (label) {
+            return `필수 입력값이 누락되었습니다: ${label}`;
+          }
+        } catch {
+          // 라벨 조회 실패 시 컬럼명으로 폴백
+        }
+      }
+      const detail = colName ? ` [${colName}]` : "";
+      return `필수 입력값이 누락되었습니다.${detail}`;
+    }
+    case "23505":
+      return "중복된 데이터가 존재합니다.";
+    case "23503":
+      return "참조 무결성 제약 조건 위반입니다.";
+    default:
+      if (error.code.startsWith("23")) {
+        return "데이터 무결성 제약 조건 위반입니다.";
+      }
+      return error.message || "데이터 처리 중 오류가 발생했습니다.";
+  }
+}