move instantiation of date time immutable to use case. request gets a string

app/Plan/UseCases/CreatePlan.php

@@ -59,7 +59,7 @@ class CreatePlan
         foreach ($nodesOfText as $node) {
             $this->createScheduledNode->execute(
                 new CreateScheduledNodeRequest(
-                    date: new DateTimeImmutable(),
+                    date: '2025-01-01', // TODO: this should be cycling over some list of dates
                     planId: $plan->getId(),
                 )
             );