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/documents/[id]/edit/+page.server.ts

@@ -60,6 +60,53 @@ export const actions = {
 		throw redirect(303, `/documents/${params.id}`);
 	},
 
+	markForReview: async ({
+		params,
+		fetch
+	}: {
+		params: { id: string };
+		fetch: typeof globalThis.fetch;
+	}) => {
+		const baseUrl = env.API_INTERNAL_URL || 'http://localhost:8080';
+		const api = createApiClient(fetch);
+
+		// Fetch current document to preserve all existing fields
+		const docResult = await api.GET('/api/documents/{id}', { params: { path: { id: params.id } } });
+		if (!docResult.response.ok) {
+			const code = (docResult.error as unknown as { code?: string })?.code;
+			return fail(docResult.response.status, { error: getErrorMessage(code) });
+		}
+
+		const doc = docResult.data!;
+		const formData = new FormData();
+		if (doc.title) formData.set('title', doc.title);
+		if (doc.documentDate) formData.set('documentDate', doc.documentDate);
+		if (doc.location) formData.set('location', doc.location);
+		if (doc.documentLocation) formData.set('documentLocation', doc.documentLocation);
+		if (doc.transcription) formData.set('transcription', doc.transcription);
+		if (doc.summary) formData.set('summary', doc.summary);
+		if (doc.sender?.id) formData.set('senderId', doc.sender.id);
+		if (doc.receivers?.length) {
+			doc.receivers.forEach((r: { id: string }) => formData.append('receiverIds', r.id));
+		}
+		if (doc.tags?.length) {
+			formData.set('tags', doc.tags.map((t: { name: string }) => t.name).join(','));
+		}
+		formData.set('metadataComplete', 'false');
+
+		const res = await fetch(`${baseUrl}/api/documents/${params.id}`, {
+			method: 'PUT',
+			body: formData
+		});
+
+		if (!res.ok) {
+			const backendError = await parseBackendError(res);
+			return fail(res.status, { error: getErrorMessage(backendError?.code) });
+		}
+
+		throw redirect(303, `/documents/${params.id}`);
+	},
+
 	delete: async ({ params, fetch }) => {
 		const baseUrl = env.API_INTERNAL_URL || 'http://localhost:8080';