Rebuild admin pages around DataTable/AdminModal; restructure categories/groups and v2 groups API

Remove the generic $lib/svelte-admin CRUD layer and AdminTable.svelte; each
admin route now owns its own form/modal logic. Add DataTable.svelte,
superform-errors.ts, and profile-specific modal/field components.

Flatten proclamation categories/groups and drop subscription levels; add the
v2 groups API; update v1/v2 endpoints, serializers, auth, and regenerated
Prisma client with the new migrations.

Document the overhaul plan in docs/ADMIN_OVERHAUL.md.

src/routes/+error.svelte

@@ -5,12 +5,9 @@
 
 <Window>
 	{#if $page.status === 403}
-		<h1 class="dark:text-gray-100">Not Authorized</h1>
-		<p class="dark:text-gray-300">
-			You don't have permission to view this page. <a
-				href="/"
-				class="dark:text-gray-400 dark:hover:text-gray-200">Go home</a
-			>.
+		<h1>Not Authorized</h1>
+		<p>
+			You don't have permission to view this page. <a href="/">Go home</a>.
 		</p>
 	{/if}
 </Window>