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/en.json

@@ -873,5 +873,19 @@
 	"bulk_drop_zone_label": "Drop files here",
 	"bulk_remove_file": "Remove",
 	"bulk_title_single": "New Document",
-	"bulk_title_multi": "New Documents"
+	"bulk_title_multi": "New Documents",
+	"bulk_edit_button": "Bulk edit",
+	"bulk_edit_n_selected": "{count} documents selected",
+	"bulk_edit_clear_all": "Clear all",
+	"bulk_edit_all_x": "Edit all {count}",
+	"bulk_edit_select_document": "Select document {title}",
+	"bulk_edit_hint": "Only filled fields are applied. Tags and receivers are added, not replaced.",
+	"bulk_edit_badge_additive": "+ added",
+	"bulk_edit_badge_replace": "replaced",
+	"bulk_edit_save_progress": "Batch {done} of {total} processed",
+	"bulk_edit_save_partial": "{done} of {total} saved",
+	"bulk_edit_retry": "Retry",
+	"bulk_edit_title": "Bulk edit",
+	"bulk_edit_save_button": "Apply",
+	"error_bulk_edit_too_many_ids": "Maximum 500 documents per request."
 }