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.

docker-compose.gpu.yml

@@ -0,0 +1,44 @@
+
+services:
+  backend:
+    container_name: bilinote-backend
+    build:
+      context: .
+      dockerfile: backend/Dockerfile.gpu
+    env_file:
+      - .env
+    environment:
+      - BACKEND_PORT=${BACKEND_PORT}
+      - BACKEND_HOST=${BACKEND_HOST}
+    volumes:
+      - ./backend:/app
+    expose:
+      - "${BACKEND_PORT}"  # 不再对外暴露，用于 nginx 内部通信
+    deploy:
+      resources:
+        reservations:
+          devices:
+            - driver: "nvidia"
+              count: "all"
+              capabilities: ["gpu"]
+
+  frontend:
+    container_name: bilinote-frontend
+    build:
+      context: .
+      dockerfile: BillNote_frontend/Dockerfile
+    env_file:
+      - .env
+    expose:
+      - "80"  # 不暴露给宿主机，只供 nginx 访问
+
+  nginx:
+    container_name: bilinote-nginx
+    image: nginx:1.25-alpine
+    ports:
+      - "${APP_PORT}:80"
+    volumes:
+      - ./nginx/default.conf:/etc/nginx/conf.d/default.conf
+    depends_on:
+      - backend
+      - frontend