feat: update flake.lock (#99)

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/8eb28adfa3dc4de28e792e3bf49fcf9007ca8ac9?narHash=sha256-NOrUtIhTkIIumj1E/Rsv1J37Yi3xGStISEo8tZm3KW4%3D' (2025-09-05)
  → 'github:nixos/nixpkgs/c23193b943c6c689d70ee98ce3128239ed9e32d1?narHash=sha256-hLEO2TPj55KcUFUU1vgtHE9UEIOjRcH/4QbmfHNF820%3D' (2025-09-13)

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]