Add GPU support with Docker enhancements

- Introduced a `Dockerfile.gpu` for GPU-enabled backend setup.
- Added `docker-compose.gpu.yml` to utilize GPU resources via NVIDIA.
- Fixed Nginx configuration for GPU backend port changes.

backend/Dockerfile.gpu

@@ -0,0 +1,15 @@
+FROM nvidia/cuda:12.6.0-cudnn-runtime-ubuntu24.04
+
+RUN apt update && \
+    apt install -y ffmpeg python3-pip && \
+    apt clean all
+
+# 设置 Hugging Face 镜像源环境变量
+ENV HF_ENDPOINT=https://hf-mirror.com
+
+WORKDIR /app
+COPY ./backend /app
+RUN pip install --no-cache-dir -i https://pypi.mirrors.ustc.edu.cn/simple -r requirements.txt --break-system-packages
+RUN pip install --no-cache-dir -i https://pypi.mirrors.ustc.edu.cn/simple transformers[torch]>=4.23 --break-system-packages
+
+CMD ["python3", "main.py"]