First fully working user management, move to layout groups

src/routes/(main)/abrechnung/+page.svelte

@@ -0,0 +1,10 @@
+<script lang="ts">
+import Header from "$lib/components/Header.svelte";
+</script>
+
+<Header>
+<ul class=site_header slot=links>
+	<li><a href="/">Home</a></li>
+</ul>
+
+</Header>