refactor: inline single-use components, remove dead code

- Inline TopBar into root layout (+layout.svelte) — only used there
- Inline Center into home page (+page.svelte) — only used there
- Remove ComboBox.svelte — dead code, no imports
- Remove TipTap.svelte — dead code, no imports
- Remove empty container/ui/admin/tiptap directories
- Keep Window.svelte in components/containers/ — used by 4 pages

src/routes/+page.svelte

@@ -1,7 +1,3 @@
-<script lang="ts">
-	import Center from '$lib/components/containers/Center.svelte';
-</script>
-
-<Center>
+<div class="flex flex-1 flex-col items-center justify-center">
 	<h1 class="dark:text-gray-100">Hello</h1>
-</Center>
+</div>