feat: Implement approval request validation and enhance UI components

- Added validation to prevent duplicate approval requests for the same target, ensuring that only one active or completed approval exists at a time.
- Implemented a check to disallow self-approval in the approval line unless the approval type is 'self'.
- Integrated the ApprovalDetailModal component into the main layout for improved user experience.
- Updated the SalesOrderPage to include approval status in the data structure, enhancing visibility of approval states.
- Enhanced BOM management modals across multiple company implementations to accommodate new UI requirements.

backend-node/src/controllers/approvalController.ts

@@ -892,6 +892,40 @@ export class ApprovalRequestController {
       const userName = req.user?.userName || "";
       const deptName = req.user?.deptName || "";
 
+      // 🔒 중복 결재 차단: 같은 target에 활성/완료된 결재가 있으면 거부
+      // (rejected, cancelled는 재상신 허용)
+      if (target_record_id) {
+        const existing = await queryOne<any>(
+          `SELECT request_id, status FROM approval_requests
+           WHERE target_table = $1 AND target_record_id = $2 AND company_code = $3
+             AND status IN ('requested', 'in_progress', 'approved', 'post_pending')
+           ORDER BY request_id DESC LIMIT 1`,
+          [target_table, safeTargetRecordId, companyCode]
+        );
+        if (existing) {
+          const statusLabel: Record<string, string> = {
+            requested: "요청됨", in_progress: "결재중", approved: "승인완료", post_pending: "후결대기",
+          };
+          return res.status(409).json({
+            success: false,
+            message: `이미 ${statusLabel[existing.status] || existing.status} 상태의 결재가 존재합니다. (요청 ID: ${existing.request_id})`,
+            error: { code: "DUPLICATE_APPROVAL", details: existing },
+          });
+        }
+      }
+
+      // 🔒 자기 자신 결재 차단: approval_type이 'self'가 아니면 결재선에 본인 포함 불가
+      if (approval_type !== "self" && Array.isArray(approvers)) {
+        const selfInLine = approvers.find((a: any) => (a.userId || a.user_id) === userId);
+        if (selfInLine) {
+          return res.status(400).json({
+            success: false,
+            message: "결재선에 본인을 포함할 수 없습니다. 자기결재(전결)는 별도 유형을 사용해 주세요.",
+            error: { code: "SELF_APPROVER_NOT_ALLOWED" },
+          });
+        }
+      }
+
       // approval_mode를 target_record_data에 병합 저장 (하위호환)
       const mergedRecordData = {
         ...(target_record_data || {}),