Update Dockerfile

Dockerfile

@@ -13,12 +13,12 @@ COPY frontend/ .
 RUN npm run build
 
 # 阶段 2：运行后端 + 提供前端静态资源
-FROM python:3.9
+FROM python:3.9-slim
 WORKDIR /app
 
 # 后端依赖
 COPY backend/requirements.txt ./backend/requirements.txt
-RUN pip install -r backend/requirements.txt
+RUN pip install --no-cache-dir -r backend/requirements.txt
 
 # 拷贝后端代码
 COPY backend/ ./backend/
@@ -27,4 +27,4 @@ COPY backend/ ./backend/
 COPY --from=frontend-build /app/frontend/dist ./frontend_dist
 
 # 启动命令：运行后端，同时提供静态文件
-CMD ["gunicorn", "backend.app:app", "--host", "0.0.0.0", "--port", "7860"]
+CMD ["gunicorn", "-b", "0.0.0.0:7860", "backend.app:app"]