feat(WEB): 견적 시스템 개선, 엑셀 다운로드, PDF 생성 기능 추가

견적 시스템:
- QuoteRegistrationV2: 할인 모달, 거래명세서 모달, vatType 필드 추가
- DiscountModal: 할인율/할인금액 상호 계산 모달
- QuoteTransactionModal: 거래명세서 미리보기 모달
- LocationDetailPanel, LocationListPanel 개선

템플릿 기능:
- UniversalListPage: 엑셀 다운로드 기능 추가 (전체/선택 다운로드)
- DocumentViewer: PDF 생성 기능 개선

신규 API:
- /api/pdf/generate: Puppeteer 기반 PDF 생성 엔드포인트

UI 개선:
- 입력 컴포넌트 placeholder 스타일 개선 (opacity 50%)
- 각종 리스트 컴포넌트 정렬/필터링 개선

패키지 추가:
- html2canvas, jspdf, puppeteer, dom-to-image-more

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/ui/quantity-input.tsx

@@ -222,7 +222,7 @@ const QuantityInput = React.forwardRef<HTMLInputElement, QuantityInputProps>(
             data-slot="input"
             disabled={disabled}
             className={cn(
-              "file:text-foreground placeholder:text-muted-foreground selection:bg-primary selection:text-primary-foreground dark:bg-input/30 border-input flex h-9 w-full min-w-0 rounded-md border px-3 py-1 text-base bg-input-background transition-[color,box-shadow] outline-none file:inline-flex file:h-7 file:border-0 file:bg-transparent file:text-sm file:font-medium disabled:pointer-events-none disabled:cursor-not-allowed disabled:opacity-50 md:text-sm",
+              "file:text-foreground placeholder:text-muted-foreground/50 selection:bg-primary selection:text-primary-foreground dark:bg-input/30 border-input flex h-9 w-full min-w-0 rounded-md border px-3 py-1 text-base bg-input-background transition-[color,box-shadow] outline-none file:inline-flex file:h-7 file:border-0 file:bg-transparent file:text-sm file:font-medium disabled:pointer-events-none disabled:cursor-not-allowed disabled:opacity-50 md:text-sm",
               "focus-visible:border-ring focus-visible:ring-ring/50 focus-visible:ring-[3px]",
               error && "border-red-500 focus-visible:border-red-500 focus-visible:ring-red-500/20",
               showButtons && "text-center",