fix: 크롭 이미지 URL을 API 서버 기준으로 해석 + 복습 시 사용자 등록 문제 이미지 표시

- import-pdf: resolveUploadUrl로 이미지 src를 API 서버 도메인으로 변환
- review: currentProblem이 null이어도 StudyLog.imageUrl이 있으면 이미지 표시
- getOne API: correctAnswer, imageUrl 필드 응답에 추가
- api.ts: StudyLogDetail에 imageUrl 필드 추가

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/src/study-logs/study-logs.service.ts

@@ -554,6 +554,8 @@ export class StudyLogsService {
       studiedAt: log.studiedAt,
       result: log.result,
       chosenAnswer: log.chosenAnswer,
+      correctAnswer: log.correctAnswer,
+      imageUrl: log.imageUrl,
       memo: log.memo,
       timeSpent: log.timeSpent,
       difficulty: log.difficulty,

frontend/src/app/review/page.tsx

@@ -169,7 +169,7 @@ export default function ReviewPage() {
   const currentProblem = currentDetail?.problem ?? null;
   const currentPassage = currentProblem?.passage ?? null;
   const currentProblemImageUrl = resolveUploadUrl(
-    currentProblem?.imageUrl ?? currentProblem?.pageImageUrl,
+    currentProblem?.imageUrl ?? currentProblem?.pageImageUrl ?? currentDetail?.imageUrl,
   );
   const currentPassageImageUrl = resolveUploadUrl(currentPassage?.imageUrl);
   const ghostItems = queue?.slice(1, 3) ?? [];
@@ -616,7 +616,7 @@ export default function ReviewPage() {
               </CardTitle>
 
               <CardBody>
-                {currentProblem && (
+                {(currentProblem || currentProblemImageUrl) && (
                   <PromptBlock>
                     {currentPassage && (
                       <PromptPassageSection
@@ -631,20 +631,22 @@ export default function ReviewPage() {
                         }
                       />
                     )}
-                    <PromptImageButton
-                      type="button"
-                      onClick={() => setLightboxOpenFor(currentItem.id)}
-                      aria-label={`${currentProblem.problemSet.subjectName} ${currentProblem.number}번 이미지 크게 보기`}
-                    >
-                      <PromptImageStage
-                        imageUrl={currentProblemImageUrl}
-                        alt={`${currentProblem.problemSet.subjectName} ${currentProblem.number}번`}
-                      />
-                      <PromptImageHint>
-                        <Icon name="export" size={14} />
-                        눌러서 확대
-                      </PromptImageHint>
-                    </PromptImageButton>
+                    {currentProblemImageUrl && (
+                      <PromptImageButton
+                        type="button"
+                        onClick={() => setLightboxOpenFor(currentItem.id)}
+                        aria-label={`${currentProblem?.problemSet?.subjectName ?? '수학'} ${currentProblem?.number ?? ''} 이미지 크게 보기`}
+                      >
+                        <PromptImageStage
+                          imageUrl={currentProblemImageUrl}
+                          alt={`${currentProblem?.problemSet?.subjectName ?? '수학'} ${currentProblem?.number ?? ''}`}
+                        />
+                        <PromptImageHint>
+                          <Icon name="export" size={14} />
+                          눌러서 확대
+                        </PromptImageHint>
+                      </PromptImageButton>
+                    )}
                   </PromptBlock>
                 )}
 

frontend/src/app/study/import-pdf/page.tsx

@@ -17,7 +17,7 @@ import {
   Select,
   Stack,
 } from '@/components/ui/primitives';
-import { api, type StudyResult, type Subject, type Tag } from '@/lib/api';
+import { api, resolveUploadUrl, type StudyResult, type Subject, type Tag } from '@/lib/api';
 import { theme } from '@/styles/theme';
 
 interface ParsedProblem {
@@ -397,7 +397,7 @@ function ImportPdfBody() {
                       <ProblemNumber>{problem.number}번</ProblemNumber>
                       <ProblemImageWrap>
                         <ProblemImage
-                          src={problem.imageUrl}
+                          src={resolveUploadUrl(problem.imageUrl) ?? problem.imageUrl}
                           alt={`${problem.number}번 문제`}
                           loading="lazy"
                         />

frontend/src/lib/api.ts

@@ -317,6 +317,7 @@ export interface StudyLogDetail {
   result: StudyResult;
   chosenAnswer: number | null;
   correctAnswer: number | null;
+  imageUrl: string | null;
   memo: string | null;
   timeSpent: number | null;
   difficulty: number;