fix:优化试题内容和样式排版

backend/Dockerfile

@@ -1,14 +1,26 @@
-# 基础镜像来自 Docker Hub；请在本机配置阿里云镜像加速器后再构建（见仓库 docker-compose.yml 注释）
 FROM python:3.12-slim
 
 WORKDIR /app
 
 ENV PYTHONDONTWRITEBYTECODE=1
 ENV PYTHONUNBUFFERED=1
-ENV PIP_INDEX_URL=https://mirrors.aliyun.com/pypi/simple/
+# 默认直连外网 API，避免宿主机/Docker Desktop 传入的 *_PROXY 影响 httpx（需代理时在 compose 中覆盖）
+ENV HTTPX_TRUST_ENV=0
+ENV HTTP_PROXY=
+ENV HTTPS_PROXY=
+ENV ALL_PROXY=
+ENV http_proxy=
+ENV https_proxy=
+ENV all_proxy=
+ENV NO_PROXY="*"
+
+ARG PIP_INDEX_URL=https://mirrors.aliyun.com/pypi/simple/
+ARG PIP_TRUSTED_HOST=mirrors.aliyun.com
+ARG DEBIAN_MIRROR_HOST=mirrors.aliyun.com
+RUN sed -i "s/deb.debian.org/${DEBIAN_MIRROR_HOST}/g; s/security.debian.org/${DEBIAN_MIRROR_HOST}/g" /etc/apt/sources.list.d/debian.sources
 
 COPY requirements.txt /app/requirements.txt
-RUN pip install --no-cache-dir -r /app/requirements.txt
+RUN pip install --no-cache-dir -i "${PIP_INDEX_URL}" --trusted-host "${PIP_TRUSTED_HOST}" -r /app/requirements.txt
 
 COPY app /app/app