add dockerfile for nginx

Dockerfile.nginx

@@ -0,0 +1,2 @@
+FROM nginx:alpine
+COPY nginx.conf /etc/nginx/conf.d/default.conf

docker-compose.yaml

@@ -13,7 +13,8 @@ services:
       - "traefik.http.services.django-service.loadbalancer.server.port=8000"
 
   nginx:
-    image: nginx:alpine
+    context: .
+    dockerfile: Dockerfile.nginx
     volumes:
       - ./nginx.conf:/etc/nginx/conf.d/default.conf:ro
       - media_volume:/app/media:ro # ان‌جینکس فقط باید بخواند (امن‌تر)