feat(bulk-edit): add i18n keys, error mapping, and regenerate api types

- 14 new Paraglide keys in de/en/es for the bulk-edit UI strings (selection
  bar, callout, badges, save progress, retry, error)
- BULK_EDIT_TOO_MANY_IDS added to errors.ts type union and getErrorMessage()
- Regenerated api.ts now includes /api/documents/{bulk,batch-metadata,ids}
  and the DocumentBulkEditDTO / BulkEditResult / DocumentBatchSummary schemas

Refs #225

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

frontend/messages/de.json

@@ -873,5 +873,19 @@
 	"bulk_drop_zone_label": "Dateien ablegen",
 	"bulk_remove_file": "Entfernen",
 	"bulk_title_single": "Neues Dokument",
-	"bulk_title_multi": "Neue Dokumente"
+	"bulk_title_multi": "Neue Dokumente",
+	"bulk_edit_button": "Massenbearbeitung",
+	"bulk_edit_n_selected": "{count} Dokumente ausgewählt",
+	"bulk_edit_clear_all": "Alles aufheben",
+	"bulk_edit_all_x": "Alle {count} editieren",
+	"bulk_edit_select_document": "Dokument {title} auswählen",
+	"bulk_edit_hint": "Nur ausgefüllte Felder werden angewendet. Tags und Empfänger werden hinzugefügt, nicht ersetzt.",
+	"bulk_edit_badge_additive": "+ wird hinzugefügt",
+	"bulk_edit_badge_replace": "wird ersetzt",
+	"bulk_edit_save_progress": "Batch {done} von {total} verarbeitet",
+	"bulk_edit_save_partial": "{done} von {total} gespeichert",
+	"bulk_edit_retry": "Erneut versuchen",
+	"bulk_edit_title": "Massenbearbeitung",
+	"bulk_edit_save_button": "Anwenden",
+	"error_bulk_edit_too_many_ids": "Maximal 500 Dokumente pro Anfrage."
 }