Keep bulk-deleted cards in grid until next scan

Extend the keep-until-next-scan behaviour to the bulk delete modal: instead
of removing matched cards on success, mark them _deleted and keep them greyed
with a "🗑 Deleted" badge and hidden buttons. /api/delete_bulk now returns
deleted_ids so the grid marks exactly the items the server actually deleted —
partial failures stay active and re-deletable. Already-handled (_deleted /
_redacted) items are excluded from the bulk-delete match set so they aren't
re-counted or re-processed.

201 tests pass.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

routes/export.py

@@ -1758,10 +1758,11 @@ def delete_bulk():
             except Exception: pass
 
     return jsonify({
-        "ok":      True,
-        "deleted": len(deleted_ids),
-        "failed":  len(failed_items),
-        "errors":  failed_items[:10],  # cap error list
+        "ok":          True,
+        "deleted":     len(deleted_ids),
+        "deleted_ids": deleted_ids,    # so the grid can mark exactly these
+        "failed":      len(failed_items),
+        "errors":      failed_items[:10],  # cap error list
     })