refactor: admin sidebar (#18276)

web/src/lib/components/layouts/PageContent.svelte

@@ -0,0 +1,26 @@
+<script lang="ts">
+  import { Container, Scrollable, type Size } from '@immich/ui';
+  import type { Snippet } from 'svelte';
+
+  interface Props {
+    id?: string;
+    title?: string;
+    size?: Size | 'full';
+    buttons?: Snippet;
+    children?: Snippet;
+  }
+
+  let { title, size, buttons, children, id }: Props = $props();
+</script>
+
+<div class="h-full flex flex-col">
+  <div class="flex h-16 w-full place-items-center justify-between border-b p-2">
+    <div class="font-medium outline-none" tabindex="-1" {id}>{title}</div>
+    {@render buttons?.()}
+  </div>
+  <Scrollable class="grow">
+    <Container {size} class="flex flex-col p-4">
+      {@render children?.()}
+    </Container>
+  </Scrollable>
+</div>