feat(WEB): 발주처 검색 모달 추가 및 견적 할인 기능 개선

- SupplierSearchModal: 매입 가능 거래처 검색 모달 신규 생성
- QuoteRegistrationV2: 할인율/할인금액을 formData로 통합하여 저장/로드 연동
- QuoteFooterBar: view 모드에서 할인 버튼 비활성화
- types.ts: discountRate/discountAmount 필드 추가, 할인 반영 총액 계산 수정
- quote-management page: 저장 실패 시 에러 메시지 정확히 표시하도록 throw 방식 변경

src/components/quotes/QuoteFooterBar.tsx

@@ -140,10 +140,11 @@ export function QuoteFooterBar({
             </Button>
           )}
 
-          {/* 할인하기 */}
+          {/* 할인하기 - view 모드에서는 비활성 */}
           {onDiscount && (
             <Button
               onClick={onDiscount}
+              disabled={isViewMode}
               variant="outline"
               className="gap-2 px-6 border-orange-300 text-orange-600 hover:bg-orange-50"
             >

src/components/quotes/QuoteRegistrationV2.tsx

@@ -96,6 +96,8 @@ export interface QuoteFormDataV2 {
   vatType: "included" | "excluded"; // 부가세 (포함/별도)
   remarks: string; // 비고
   status: "draft" | "temporary" | "final"; // 작성중, 임시저장, 최종저장
+  discountRate: number; // 할인율 (%)
+  discountAmount: number; // 할인 금액
   locations: LocationItem[];
 }
 
@@ -133,6 +135,8 @@ const INITIAL_FORM_DATA: QuoteFormDataV2 = {
   vatType: "included", // 기본값: 부가세 포함
   remarks: "",
   status: "draft",
+  discountRate: 0,
+  discountAmount: 0,
   locations: [],
 };
 
@@ -181,8 +185,9 @@ export function QuoteRegistrationV2({
   const [transactionPreviewOpen, setTransactionPreviewOpen] = useState(false);
   const [discountModalOpen, setDiscountModalOpen] = useState(false);
   const [formulaViewOpen, setFormulaViewOpen] = useState(false);
-  const [discountRate, setDiscountRate] = useState(0);
-  const [discountAmount, setDiscountAmount] = useState(0);
+  // 할인율/할인금액은 formData에서 관리 (저장/로드 연동)
+  const discountRate = formData.discountRate ?? 0;
+  const discountAmount = formData.discountAmount ?? 0;
   const pendingAutoCalculateRef = useRef(false);
 
   // API 데이터
@@ -309,8 +314,7 @@ export function QuoteRegistrationV2({
 
   // 할인 적용 핸들러
   const handleApplyDiscount = useCallback((rate: number, amount: number) => {
-    setDiscountRate(rate);
-    setDiscountAmount(amount);
+    setFormData(prev => ({ ...prev, discountRate: rate, discountAmount: amount }));
     toast.success(`할인이 적용되었습니다. (${rate.toFixed(1)}%, ${amount.toLocaleString()}원)`);
   }, []);
 
@@ -650,7 +654,8 @@ export function QuoteRegistrationV2({
       toast.success(saveType === "temporary" ? "저장되었습니다." : "견적이 확정되었습니다.");
     } catch (error) {
       if (isNextRedirectError(error)) throw error;
-      toast.error("저장 중 오류가 발생했습니다.");
+      const message = error instanceof Error ? error.message : "저장 중 오류가 발생했습니다.";
+      toast.error(message);
     } finally {
       setIsSaving(false);
     }

src/components/quotes/types.ts

@@ -78,6 +78,8 @@ export interface Quote {
   supplyAmount: number;
   taxAmount: number;
   totalAmount: number;
+  discountRate: number;
+  discountAmount: number;
   status: QuoteStatus;
   currentRevision: number;
   isFinal: boolean;
@@ -247,6 +249,8 @@ export function transformApiToFrontend(apiData: QuoteApiData): Quote {
     supplyAmount: parseFloat(String(apiData.supply_amount)) || 0,
     taxAmount: parseFloat(String(apiData.tax_amount)) || 0,
     totalAmount: parseFloat(String(apiData.total_amount)) || 0,
+    discountRate: Number(apiData.discount_rate) || 0,
+    discountAmount: Number(apiData.discount_amount) || 0,
     status: apiData.status,
     currentRevision: apiData.current_revision || 0,
     isFinal: apiData.is_final || false,
@@ -837,10 +841,12 @@ export function transformV2ToApi(
     }));
   }
 
-  // 3. 총액 계산
+  // 3. 총액 계산 (할인 반영)
   const totalSupply = items.reduce((sum, item) => sum + item.total_price, 0);
-  const totalTax = Math.round(totalSupply * 0.1);
-  const grandTotal = totalSupply + totalTax;
+  const discountAmt = data.discountAmount || 0;
+  const discountedSupply = totalSupply - discountAmt;
+  const totalTax = Math.round(discountedSupply * 0.1);
+  const grandTotal = discountedSupply + totalTax;
 
   // 4. API 요청 객체 반환
   return {
@@ -858,7 +864,7 @@ export function transformV2ToApi(
     unit_symbol: '개소',
     total_amount: grandTotal,
     discount_rate: data.discountRate || 0,
-    discount_amount: data.discountAmount || 0,
+    discount_amount: discountAmt,
     status: data.status === 'final' ? 'finalized' : 'draft',
     is_final: data.status === 'final',
     calculation_inputs: calculationInputs,
@@ -955,6 +961,8 @@ export function transformApiToV2(apiData: QuoteApiData): QuoteFormDataV2 {
     managerContact?: string;
     deliveryDate?: string;
     description?: string;
+    discountRate?: number;
+    discountAmount?: number;
   };
 
   return {
@@ -978,8 +986,9 @@ export function transformApiToV2(apiData: QuoteApiData): QuoteFormDataV2 {
     // raw API: remarks || description, transformed: description
     remarks: apiData.remarks || apiData.description || transformed.description || '',
     status: mapStatus(apiData.status),
-    discountRate: Number(apiData.discount_rate) || 0,
-    discountAmount: Number(apiData.discount_amount) || 0,
+    // raw API: discount_rate, transformed: discountRate
+    discountRate: Number(apiData.discount_rate) || transformed.discountRate || 0,
+    discountAmount: Number(apiData.discount_amount) || transformed.discountAmount || 0,
     locations: locations,
   };
 }