feat: 更新Dockerfile使用国内镜像源，添加PDF_CLEANUP_DAYS配置，添加正式环境配置文档

backend/Dockerfile

@@ -5,13 +5,24 @@ ENV PYTHONUNBUFFERED=1
 
 WORKDIR /app
 
-RUN apt-get update \
-    && apt-get install -y --no-install-recommends curl default-mysql-client fonts-noto-cjk \
+RUN sed -i 's/deb.debian.org/mirrors.aliyun.com/g' /etc/apt/sources.list.d/debian.sources \
+    && apt-get update \
+    && apt-get install -y --no-install-recommends \
+       curl \
+       default-mysql-client \
+       fonts-noto-cjk \
+       fonts-unifont \
+       libfontconfig1 \
+       libnss3 \
+       libxss1 \
+       libasound2 \
+       libatk-bridge2.0-0 \
+       libgtk-3-0 \
     && rm -rf /var/lib/apt/lists/*
 
 COPY requirements.txt .
-RUN pip install --no-cache-dir -r requirements.txt \
-    && python -m playwright install --with-deps chromium
+RUN pip install --no-cache-dir -r requirements.txt -i https://mirrors.aliyun.com/pypi/simple/ \
+    && python -m playwright install chromium
 
 COPY app ./app