fix port for mysql server

backend/docker-compose.yml

@@ -8,7 +8,7 @@ services:
     env_file: .env
     command: ["mysqld", "--authentication-policy=mysql_native_password"]
     ports:
-      - "3307:3306"
+      - "3306:3306"
     volumes:
       - mysql-db:/var/lib/mysql