refactor migrations sql scripts

migrations/20240530193528_hersteller.up.sql

@@ -1,4 +1,6 @@
 CREATE TABLE IF NOT EXISTS hersteller (
     id UUID PRIMARY KEY,
-    herstellername VARCHAR NOT NULL
+    herstellername VARCHAR NOT NULL,
+    erstellt_am TIMESTAMP WITH TIME ZONE NOT NULL,
+    geaendert_am TIMESTAMP WITH TIME ZONE NOT NULL
 );