move element seeding into its own seeder file

backend/database/seeders/ElementSeeder.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace Database\Seeders;
+
+use App\Element\CreateElementDto;
+use App\Element\ElementRepository;
+use App\Set\SetRepository;
+use Illuminate\Database\Seeder;
+
+class ElementSeeder extends Seeder
+{
+    public function run(): void
+    {
+        $setRepository = app(SetRepository::class);
+        $elementRepository = app(ElementRepository::class);
+        $baderechSet = $setRepository->find(1);
+        $elementRepository->create(new CreateElementDto(
+            set: $baderechSet,
+            title: $baderechSet->getName(),
+            parentElement: null,
+        ));
+    }
+}