feat(enrich): add metadata enrichment queue UI

Home page shows "Needs metadata" card when incomplete documents exist.
/enrich list shows all incomplete documents; /enrich/[id] provides a
split PDF-preview + compact form view with Skip / Save / Save & reviewed
actions that auto-advance through the queue.

New document page gets Save vs Save & reviewed split. Edit page gets
"Mark for review" secondary button to push a document back into the queue.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/routes/enrich/done/+page.svelte

@@ -0,0 +1,40 @@
+<script lang="ts">
+import { m } from '$lib/paraglide/messages.js';
+</script>
+
+<div class="mx-auto max-w-4xl px-4 py-10">
+	<div
+		class="border-brand-sand flex flex-col items-center justify-center rounded-sm border bg-white py-20 text-center shadow-sm"
+	>
+		<img
+			src="/degruyter-icons/Simple/Large-32px/SVG/Action/Check/Check-Circle-LG.svg"
+			alt=""
+			aria-hidden="true"
+			class="mb-6 h-16 w-16"
+		/>
+
+		<h1 class="font-serif text-2xl font-medium text-brand-navy">
+			{m.enrich_done_heading()}
+		</h1>
+
+		<p class="mt-2 max-w-xs font-sans text-sm text-gray-500">
+			{m.enrich_done_body()}
+		</p>
+
+		<div class="mt-8 flex flex-col items-center gap-4">
+			<a
+				href="/"
+				class="bg-brand-navy px-6 py-2 font-sans text-xs font-bold tracking-widest text-white uppercase transition-colors hover:bg-brand-navy/90"
+			>
+				{m.btn_back_to_overview()}
+			</a>
+
+			<a
+				href="/enrich"
+				class="font-sans text-xs text-gray-400 underline-offset-4 transition-colors hover:text-brand-navy hover:underline"
+			>
+				{m.enrich_back_to_list()}
+			</a>
+		</div>
+	</div>
+</div>