fix(docker): shared 심링크 /usr/shared 추가 — routes depth 3 대응

routes/ 하위 파일에서 ../../../shared/는 /usr/shared를 참조.
기존 /usr/src/shared 심링크만으로 부족. /usr/shared 추가.

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

system2-report/api/Dockerfile

@@ -12,7 +12,7 @@ RUN npm install --omit=dev
 
 COPY system2-report/api/ ./
 
-RUN ln -s /usr/src/app/shared /usr/src/shared
+RUN ln -s /usr/src/app/shared /usr/src/shared && ln -s /usr/src/app/shared /usr/shared
 RUN mkdir -p logs uploads
 RUN chown -R node:node /usr/src/app
 USER node