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/messages/de.json

@@ -274,5 +274,21 @@
 	"upload_duplicate": "{filename} existiert bereits —",
 	"upload_duplicate_link": "Zum Dokument",
 	"upload_invalid_type": "{filename}: Dateiformat nicht unterstützt",
-	"upload_error": "Fehler beim Hochladen von {filename}"
+	"upload_error": "Fehler beim Hochladen von {filename}",
+	"enrich_list_back": "Zurück zur Übersicht",
+	"enrich_list_count": "Dokumente",
+	"btn_save_and_mark_reviewed": "Speichern & abschließen",
+	"btn_mark_for_review": "Zur Überprüfung markieren",
+	"enrich_needs_metadata_title": "Dokumente ohne Metadaten",
+	"enrich_needs_metadata_count": "{count} Dokument(e) warten auf Metadaten",
+	"enrich_needs_metadata_cta": "Jetzt vervollständigen",
+	"enrich_list_heading": "Dokumente ohne Metadaten",
+	"enrich_list_empty_heading": "Alle Dokumente vollständig",
+	"enrich_list_empty_body": "Es gibt keine Dokumente, die noch Metadaten benötigen.",
+	"enrich_list_start": "Überprüfung starten",
+	"enrich_progress": "{count} verbleibend",
+	"enrich_skip": "Überspringen",
+	"enrich_done_heading": "Alles erledigt!",
+	"enrich_done_body": "Alle Dokumente wurden bearbeitet.",
+	"enrich_back_to_list": "Zurück zur Liste"
 }

frontend/messages/en.json

@@ -274,5 +274,21 @@
 	"upload_duplicate": "{filename} already exists —",
 	"upload_duplicate_link": "View document",
 	"upload_invalid_type": "{filename}: unsupported file format",
-	"upload_error": "Error uploading {filename}"
+	"upload_error": "Error uploading {filename}",
+	"enrich_list_back": "Back to overview",
+	"enrich_list_count": "documents",
+	"btn_save_and_mark_reviewed": "Save & mark as reviewed",
+	"btn_mark_for_review": "Mark for review",
+	"enrich_needs_metadata_title": "Documents without metadata",
+	"enrich_needs_metadata_count": "{count} document(s) waiting for metadata",
+	"enrich_needs_metadata_cta": "Complete now",
+	"enrich_list_heading": "Documents without metadata",
+	"enrich_list_empty_heading": "All documents complete",
+	"enrich_list_empty_body": "There are no documents that still need metadata.",
+	"enrich_list_start": "Start reviewing",
+	"enrich_progress": "{count} remaining",
+	"enrich_skip": "Skip",
+	"enrich_done_heading": "All done!",
+	"enrich_done_body": "All documents have been processed.",
+	"enrich_back_to_list": "Back to list"
 }

frontend/messages/es.json

@@ -274,5 +274,21 @@
 	"upload_duplicate": "{filename} ya existe —",
 	"upload_duplicate_link": "Ver documento",
 	"upload_invalid_type": "{filename}: formato de archivo no admitido",
-	"upload_error": "Error al subir {filename}"
+	"upload_error": "Error al subir {filename}",
+	"enrich_list_back": "Volver a la vista general",
+	"enrich_list_count": "documentos",
+	"btn_save_and_mark_reviewed": "Guardar y marcar como revisado",
+	"btn_mark_for_review": "Marcar para revisión",
+	"enrich_needs_metadata_title": "Documentos sin metadatos",
+	"enrich_needs_metadata_count": "{count} documento(s) esperando metadatos",
+	"enrich_needs_metadata_cta": "Completar ahora",
+	"enrich_list_heading": "Documentos sin metadatos",
+	"enrich_list_empty_heading": "Todos los documentos completos",
+	"enrich_list_empty_body": "No hay documentos que necesiten metadatos.",
+	"enrich_list_start": "Comenzar revisión",
+	"enrich_progress": "{count} restante(s)",
+	"enrich_skip": "Omitir",
+	"enrich_done_heading": "¡Todo listo!",
+	"enrich_done_body": "Todos los documentos han sido procesados.",
+	"enrich_back_to_list": "Volver a la lista"
 }