build: integrate frontend build into Nginx Dockerfile, remove separate frontend image

docker-compose.yml

@@ -53,8 +53,8 @@ services:
   nginx:
     image: ${CI_REGISTRY_URL:-git.allucanget.biz}/${CI_REGISTRY_NAMESPACE:-zwitschi/linearvoid}/nginx:latest
     build:
-      context: ./infrastructure/nginx
-      dockerfile: Dockerfile
+      context: .
+      dockerfile: infrastructure/nginx/Dockerfile
     container_name: linearvoid-nginx
     restart: unless-stopped
     ports: