fix: give postgres volume a name

docker-compose.yml

@@ -3,6 +3,9 @@ name: miniplan
 networks:
   backend:
 
+volumes:
+  postgres:
+
 services:
   db:
     image: postgres:16
@@ -13,6 +16,8 @@ services:
       - POSTGRES_DB=minis
     networks:
       - backend
+    volumes:
+      - postgres:/var/lib/postgresql/data
     healthcheck:
       test: ["CMD-SHELL", "pg_isready", "-d", "db_prod"]
       interval: 30s