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/+page.server.ts

@@ -12,7 +12,7 @@ export async function load({ url, fetch }) {
 	const api = createApiClient(fetch);
 
 	try {
-		const [docsResult, personsResult] = await Promise.all([
+		const [docsResult, personsResult, incompleteCountResult] = await Promise.all([
 			api.GET('/api/documents/search', {
 				params: {
 					query: {
@@ -25,7 +25,8 @@ export async function load({ url, fetch }) {
 					}
 				}
 			}),
-			api.GET('/api/persons')
+			api.GET('/api/persons'),
+			api.GET('/api/documents/incomplete-count')
 		]);
 
 		if (docsResult.response.status === 401 || personsResult.response.status === 401) {
@@ -39,8 +40,13 @@ export async function load({ url, fetch }) {
 		const senderObj = allPersons.find((p) => p.id === senderId);
 		const receiverObj = allPersons.find((p) => p.id === receiverId);
 
+		const incompleteCount = incompleteCountResult.response.ok
+			? (incompleteCountResult.data?.count ?? 0)
+			: 0;
+
 		return {
 			documents,
+			incompleteCount,
 			initialValues: {
 				senderName: senderObj ? `${senderObj.firstName} ${senderObj.lastName}` : '',
 				receiverName: receiverObj ? `${receiverObj.firstName} ${receiverObj.lastName}` : ''
@@ -53,6 +59,7 @@ export async function load({ url, fetch }) {
 		console.error('Error loading data:', e);
 		return {
 			documents: [],
+			incompleteCount: 0,
 			initialValues: { senderName: '', receiverName: '' },
 			filters: { q, from, to, senderId, receiverId, tags },
 			error: 'Daten konnten nicht geladen werden.' as string | null