--- token/ERC721/ERC721.sol	2025-08-19 17:23:33.436823903 +0200
+++ token/ERC721/ERC721.sol	2025-08-19 17:23:07.328925282 +0200
@@ -27,7 +27,7 @@
 
     mapping(uint256 tokenId => address) private _owners;
 
-    mapping(address owner => uint256) private _balances;
+    mapping(address owner => uint256) internal _balances; // private → internal for FV
 
     mapping(uint256 tokenId => address) private _tokenApprovals;