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/app.html

@@ -3,23 +3,10 @@
 	<head>
 		<meta charset="utf-8" />
 		<meta name="viewport" content="width=device-width, initial-scale=1" />
-		<script>
-			(function () {
-				const theme = localStorage.getItem('theme');
-				if (
-					theme === 'dark' ||
-					(!theme && window.matchMedia('(prefers-color-scheme: dark)').matches)
-				) {
-					document.documentElement.classList.add('dark');
-				} else {
-					document.documentElement.classList.remove('dark');
-				}
-			})();
-		</script>
 		%sveltekit.head%
 	</head>
 
-	<body class="m-0" data-sveltekit-preload-data="hover">
-		<div class="flex h-dvh w-dvw flex-col">%sveltekit.body%</div>
+	<body data-sveltekit-preload-data="hover">
+		<div>%sveltekit.body%</div>
 	</body>
 </html>