feat: 히스토리 내역을 통한 뒤로가기 분기 처리

src/feature/album/4cut/components/ScreenAlbum4Cut.tsx

@@ -20,6 +20,7 @@ import { useQueryClient } from '@tanstack/react-query';
 import { Download, Loader2, LucideIcon, Menu, Send } from 'lucide-react';
 import dynamic from 'next/dynamic';
 import Link from 'next/link';
+import { useRouter } from 'next/navigation';
 import { useEffect, useRef, useState } from 'react';
 import { useGetAlbumInfo } from '../../detail/hooks/useGetAlbumInfo';
 import { use4CutAiSummary } from '../hooks/use4CutAiSummary';
@@ -37,11 +38,34 @@ interface ScreenAlbum4CutProps {
 }
 
 export default function ScreenAlbum4Cut({ albumId }: ScreenAlbum4CutProps) {
+  const router = useRouter();
   const queryClient = useQueryClient();
   const [isCaptureVisible, setIsCaptureVisible] = useState(false);
   const [isDownloading, setIsDownloading] = useState(false);
   const [showExplanation, setShowExplanation] = useState(false);
   const captureRef = useRef<HTMLDivElement>(null);
+
+  const handleBackClick = () => {
+    if (typeof window === 'undefined') return;
+    // 공유 링크 등 외부 유입 시 외부 사이트로 되돌아가는 것을 방지합니다.
+    const isNewTab = window.history.length <= 1 || !document.referrer;
+    // referrer가 우리 서비스 origin일 때만 안전한 내부 이동으로 봅니다.
+    const isInternalReferrer = (() => {
+      if (!document.referrer) return false;
+      try {
+        return new URL(document.referrer).origin === window.location.origin;
+      } catch {
+        return false;
+      }
+    })();
+
+    if (isNewTab || !isInternalReferrer) {
+      // 히스토리/리퍼러가 신뢰되지 않으면 안전한 내부 경로로 보냅니다.
+      router.push('/main');
+    } else {
+      router.back();
+    }
+  };
   const { data } = useGetAlbumInfo(albumId);
   const { data: albumInformData } = useGetAlbumInform({ code: albumId });
   const { data: { name } = {} } = useGetUserMe();
@@ -201,6 +225,7 @@ export default function ScreenAlbum4Cut({ albumId }: ScreenAlbum4CutProps) {
     <>
       <CustomHeader
         isShowBack
+        onBackClick={handleBackClick}
         title={data?.title ?? ''}
         rightContent={
           <div className='flex gap-4'>