AI分析Markdown渲染间距优化，去除pre-wrap双重间距；Dockerfile npm换国内镜像

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/backend/Dockerfile

@@ -5,7 +5,8 @@ WORKDIR /ui
 
 # 优先拷贝 package.json 命中 layer cache;无 lock 时退回 npm install
 COPY frontend/package*.json ./
-RUN if [ -f package-lock.json ]; then npm ci; else npm install; fi
+RUN npm config set registry https://registry.npmmirror.com && \
+    if [ -f package-lock.json ]; then npm ci; else npm install; fi
 
 COPY frontend ./
 RUN npm run build