fix(docker): install libreoffice-writer so Rich-mode Office rendering (.docx/.odt/.rtf) works on the deployed container

Dockerfile

@@ -1,24 +1,13 @@
 # EPUB3 -> PDF converter (Flask + WeasyPrint) — Coolify / any Docker host
 # WeasyPrint needs pango + fontconfig system libraries; CJK fonts for full-text support.
+# Rich mode: the Office trio (.docx/.odt/.rtf) renders through LibreOffice headless.
+# libreoffice-writer covers all three and provides /usr/bin/libreoffice; its dependency
+# pulls in the core soffice engine. Installed lean via --no-install-recommends.
 FROM python:3.12-slim
 
-ENV PYTHONDONTWRITEBYTECODE=1 \
-    PYTHONUNBUFFERED=1 \
-    PORT=8030 \
-    DATA_DIR=/app/data \
-    PIP_NO_CACHE_DIR=1
+ENV PYTHONDONTWRITEBYTECODE=1 PYTHONUNBUFFERED=1 PORT=8030 DATA_DIR=/app/data PIP_NO_CACHE_DIR=1
 
-RUN apt-get update && apt-get install -y --no-install-recommends \
-    libpango-1.0-0 \
-    libpangoft2-1.0-0 \
-    libharfbuzz0b \
-    libffi8 \
-    shared-mime-info \
-    fontconfig \
-    fonts-dejavu-core \
-    fonts-noto-cjk \
-    pandoc \
-    && rm -rf /var/lib/apt/lists/* && fc-cache -f
+RUN apt-get update && apt-get install -y --no-install-recommends libpango-1.0-0 libpangoft2-1.0-0 libharfbuzz0b libffi8 shared-mime-info fontconfig fonts-dejavu-core fonts-noto-cjk pandoc libreoffice-writer && rm -rf /var/lib/apt/lists/* && fc-cache -f
 
 WORKDIR /app