fix: named volume for sl postgres

simplelogin/docker-compose.yml

@@ -18,7 +18,7 @@ services:
       POSTGRES_PASSWORD_FILE: /run/secrets/POSTGRES_PASSWORD
       POSTGRES_DB: simplelogin
     volumes:
-      - ./data/postgres:/var/lib/postgresql/data
+      - postgres_data:/var/lib/postgresql/data
     networks:
       - default
 
@@ -143,3 +143,7 @@ services:
 networks:
   default:
     driver: bridge
+
+volumes:
+  postgres_data:
+    driver: local