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/[id]/+page.svelte

@@ -0,0 +1,162 @@
+<script lang="ts">
+import { enhance } from '$app/forms';
+import { untrack } from 'svelte';
+import { m } from '$lib/paraglide/messages.js';
+import DocumentViewer from '$lib/components/DocumentViewer.svelte';
+import WhoWhenSection from '$lib/components/document/WhoWhenSection.svelte';
+import DescriptionSection from '$lib/components/document/DescriptionSection.svelte';
+
+let { data, form } = $props();
+
+const doc = $derived(data.document);
+
+// File preview state
+let fileUrl = $state('');
+let fileError = $state('');
+let isLoading = $state(false);
+
+// Dummy bindable state required by DocumentViewer
+let annotateMode = $state(false);
+let activeAnnotationId = $state<string | null>(null);
+let activeAnnotationPage = $state<number | null>(null);
+
+$effect(() => {
+	if (doc?.id && doc?.filePath) {
+		loadFile(doc.id);
+	}
+});
+
+async function loadFile(id: string) {
+	isLoading = true;
+	fileError = '';
+	fileUrl = '';
+	try {
+		const response = await fetch(`/api/documents/${id}/file`);
+		if (!response.ok) throw new Error('Fehler');
+		const blob = await response.blob();
+		fileUrl = URL.createObjectURL(blob);
+	} catch {
+		fileError = m.doc_file_error_preview();
+	} finally {
+		isLoading = false;
+	}
+}
+
+// Form state
+let tags = $state(untrack(() => doc.tags?.map((t: { name: string }) => t.name) ?? []));
+let senderId = $state(untrack(() => doc.sender?.id ?? ''));
+let selectedReceivers = $state(untrack(() => doc.receivers ?? []));
+</script>
+
+<svelte:head>
+	<title>{doc.title || doc.originalFilename || 'Dokument'} — Anreicherung</title>
+</svelte:head>
+
+<div class="flex h-[calc(100vh-68px)] flex-col">
+	<!-- Top bar -->
+	<div class="flex items-center justify-between border-b border-line bg-surface px-6 py-3">
+		<a
+			href="/enrich"
+			class="group inline-flex items-center font-sans text-xs font-bold tracking-widest text-ink-2 uppercase transition-colors hover:text-ink"
+		>
+			<img
+				src="/degruyter-icons/Simple/Medium-24px/SVG/Action/Arrow/Arrow-Left-MD.svg"
+				alt=""
+				aria-hidden="true"
+				class="mr-2 h-4 w-4 transform transition-transform group-hover:-translate-x-1"
+			/>
+			{m.enrich_back_to_list()}
+		</a>
+
+		<p class="max-w-sm truncate text-center font-serif text-sm font-medium text-ink">
+			{doc.title || doc.originalFilename}
+		</p>
+
+		<p class="font-sans text-xs text-ink-3">
+			{m.enrich_progress({ count: data.incompleteCount })}
+		</p>
+	</div>
+
+	<!-- Main content -->
+	<div class="flex flex-1 overflow-hidden">
+		<!-- Left: PDF preview (60%) -->
+		<div class="relative flex-[6] overflow-hidden border-r border-line">
+			<DocumentViewer
+				doc={doc}
+				fileUrl={fileUrl}
+				isLoading={isLoading}
+				error={fileError}
+				bind:annotateMode={annotateMode}
+				bind:activeAnnotationId={activeAnnotationId}
+				bind:activeAnnotationPage={activeAnnotationPage}
+				onAnnotationClick={() => {}}
+			/>
+		</div>
+
+		<!-- Right: form (40%) -->
+		<div class="flex flex-[4] flex-col overflow-hidden">
+			{#if form?.error}
+				<div class="border-b border-red-200 bg-red-50 px-6 py-3 text-sm text-red-700">
+					{form.error}
+				</div>
+			{/if}
+
+			<form
+				id="save-form"
+				method="POST"
+				action="?/save"
+				enctype="multipart/form-data"
+				use:enhance
+				class="flex-1 space-y-5 overflow-y-auto p-6"
+			>
+				<WhoWhenSection
+					bind:senderId={senderId}
+					bind:selectedReceivers={selectedReceivers}
+					initialDateIso={doc.documentDate ?? ''}
+					initialLocation={doc.location ?? ''}
+					initialSenderName={doc.sender
+						? `${doc.sender.firstName} ${doc.sender.lastName}`
+						: ''}
+				/>
+				<DescriptionSection bind:tags={tags} initialTitle={doc.title ?? ''} titleRequired={true} />
+			</form>
+
+			<!-- Skip form (outside main form to avoid nesting) -->
+			<form id="skip-form" method="POST" action="?/skip" use:enhance></form>
+
+			<!-- Action bar -->
+			<div class="flex items-center justify-between gap-3 border-t border-line bg-surface p-4">
+				<!-- Skip button linked to skip-form -->
+				<button
+					type="submit"
+					form="skip-form"
+					class="font-sans text-sm font-medium text-brand-navy/60 transition-colors hover:text-brand-navy"
+				>
+					{m.enrich_skip()}
+				</button>
+
+				<div class="flex items-center gap-3">
+					<!-- Save -->
+					<button
+						type="submit"
+						form="save-form"
+						formaction="?/save"
+						class="rounded-sm border border-gray-300 px-5 py-2 font-sans text-xs font-bold tracking-widest text-gray-600 uppercase transition-colors hover:bg-gray-50"
+					>
+						{m.btn_save()}
+					</button>
+
+					<!-- Save & mark as reviewed -->
+					<button
+						type="submit"
+						form="save-form"
+						formaction="?/saveAndReview"
+						class="rounded-sm bg-brand-navy px-5 py-2 font-sans text-xs font-bold tracking-widest text-white uppercase transition-colors hover:bg-brand-navy/90"
+					>
+						{m.btn_save_and_mark_reviewed()}
+					</button>
+				</div>
+			</div>
+		</div>
+	</div>
+</div>