build(docker): 优化 Dockerfile 以实现多阶段构建

将 Dockerfile 修改为多阶段构建，以减小最终镜像的体积并提高构建效率。

第一阶段（builder）负责安装 Python 依赖项。
第二阶段创建最终的生产镜像，仅从构建器阶段复制已安装的依赖包和应用程序代码，不包含构建时的工具和缓存。

这种方法可以显著减小镜像大小，并利用 Docker 的层缓存机制，仅在 `requirements.txt` 发生变化时才重新安装依赖。

Author: snailyp

Dockerfile

@@ -1,13 +1,29 @@
-FROM python:3.10-slim
+# Stage 1: Build dependencies
+FROM python:3.10-slim AS builder
 
 WORKDIR /app
 
-# 复制所需文件到容器中
-COPY ./requirements.txt /app
-COPY ./VERSION /app
+# Upgrade pip and setuptools
+RUN pip install --upgrade pip setuptools
 
+# Copy and install requirements
+# This layer is cached and only re-runs when requirements.txt changes
+COPY ./requirements.txt /app/
 RUN pip install --no-cache-dir -r requirements.txt
+
+# Stage 2: Final application image
+FROM python:3.10-slim
+
+WORKDIR /app
+
+# Copy installed packages from the builder stage
+COPY --from=builder /usr/local/lib/python3.10/site-packages /usr/local/lib/python3.10/site-packages
+
+# Copy the application code
 COPY ./app /app/app
+COPY ./VERSION /app
+
+# Set environment variables
 ENV API_KEYS='["your_api_key_1"]'
 ENV ALLOWED_TOKENS='["your_token_1"]'
 ENV TZ='Asia/Shanghai'