Refactor admin to shared generic CRUD; restructure proclamation categories/groups and APIs

- Replace per-model admin forms with the shared generic AdminTable/AdminModal CRUD
- Add ProclamationGroup model and admin + API v2 routes (replaces subscription levels)
- Drop subscription levels and flatten proclamation categories
- Update v2 serializers and seed data accordingly

src/routes/(protected)/admin/+error.svelte

@@ -4,22 +4,17 @@
 </script>
 
 <Window>
-	<div class="flex flex-col items-center gap-4 p-6 text-center">
-		<h1 class="text-xl font-bold text-gray-900 dark:text-gray-100">
+	<div>
+		<h1>
 			Admin Error ({$page.status})
 		</h1>
-		<p class="max-w-md text-sm text-gray-600 dark:text-gray-400">
+		<p>
 			{#if $page.error?.message}
 				{$page.error.message}
 			{:else}
 				An unexpected error occurred while loading this admin page.
 			{/if}
 		</p>
-		<a
-			href="/admin"
-			class="mt-2 border border-gray-200 px-4 py-2 text-sm font-medium text-gray-900 hover:bg-gray-50 dark:border-gray-700 dark:text-gray-100 dark:hover:bg-gray-800"
-		>
-			Back to Admin
-		</a>
+		<a href="/admin"> Back to Admin </a>
 	</div>
 </Window>