chore: add dummy postgres service for portainer debugging

- Added a simple postgres service to test if Portainer is successfully pulling and applying stack updates from the repository.

docker-compose.yml

@@ -61,6 +61,15 @@ services:
     networks:
       - fasto-net
 
+  test-postgres:
+    image: postgres:15-alpine
+    environment:
+      POSTGRES_PASSWORD: dummy_password
+    deploy:
+      replicas: 1
+    networks:
+      - fasto-net
+
 volumes:
   db_data: