fix: LibreOffice 한글/CJK 폰트 추가 (fonts-noto-cjk, fonts-nanum)

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

app/Dockerfile

@@ -2,9 +2,11 @@ FROM python:3.11-slim
 
 WORKDIR /app
 
-# LibreOffice headless (PDF 변환용)
+# LibreOffice headless (PDF 변환용) + 한글/CJK 폰트
 RUN apt-get update && \
-    apt-get install -y --no-install-recommends libreoffice-core libreoffice-calc libreoffice-writer libreoffice-impress && \
+    apt-get install -y --no-install-recommends \
+      libreoffice-core libreoffice-calc libreoffice-writer libreoffice-impress \
+      fonts-noto-cjk fonts-noto-cjk-extra fonts-nanum && \
     apt-get clean && rm -rf /var/lib/apt/lists/*
 
 COPY requirements.txt .