flake.lock: Update

Flake lock file updates:

• Updated input 'flake-parts':
    'github:hercules-ci/flake-parts/9305fe4e5c2a6fcf5ba6a3ff155720fbe4076569?narHash=sha256-tYBdgS56eXYaWVW3fsnPQ/nFlgWi/Z2Ymhyu21zVM98%3D' (2025-06-08)
  → 'github:hercules-ci/flake-parts/77826244401ea9de6e3bac47c2db46005e1f30b5?narHash=sha256-Tyw1RjYEsp5scoigs1384gIg6e0GoBVjms4aXFfRssQ%3D' (2025-07-01)
• Updated input 'nixpkgs':
    'git+https://github.com/NixOS/nixpkgs?ref=nixos-unstable-small&rev=650e71cbf76de8dd16f5648a96981b726c4ef8fe&shallow=1' (2025-06-29)
  → 'git+https://github.com/NixOS/nixpkgs?ref=nixos-unstable-small&rev=12d516726903aae3c89fe2b6b65a6880c7101c25&shallow=1' (2025-07-02)

Author: github-actions[bot]