fix: add China mirror for Alpine and pip

Dockerfile

@@ -1,12 +1,15 @@
 FROM python:3.11-alpine
 
-# 安装 ffmpeg（alpine 版很小）
+# 配置 Alpine 国内镜像源
+RUN sed -i 's/dl-cdn.alpinelinux.org/mirrors.aliyun.com/g' /etc/apk/repositories
+
+# 安装 ffmpeg
 RUN apk add --no-cache ffmpeg
 
 WORKDIR /app
 
 COPY requirements.txt .
-RUN pip install --no-cache-dir -r requirements.txt
+RUN pip install --no-cache-dir -i https://pypi.tuna.tsinghua.edu.cn/simple -r requirements.txt
 
 COPY app/ .