Update Dockerfile

Dockerfile

@@ -24,7 +24,7 @@ RUN pip install -r backend/requirements.txt
 COPY backend/ ./backend/
 
 # 拷贝前端打包好的静态资源
-COPY --from=frontend-build /app/frontend/dist ./frontend_dist
+COPY --from=frontend-build /app/frontend/dist /app/backend/frontend_dist
 
 # 启动命令：运行后端，同时提供静态文件
 CMD ["gunicorn", "-b", "0.0.0.0:7860", "backend.app:app"]