flake.lock: Update

Flake lock file updates:

• Updated input 'hercules-ci-effects':
    'github:hercules-ci/hercules-ci-effects/5f2e09654b2e70ba643e41609d9f9b6640f22113?narHash=sha256-CNBgr4OZSuklGtNOa9CnTNo9%2BXceqn/EDAC1Tc43fH8%3D' (2025-07-15)
  → 'github:hercules-ci/hercules-ci-effects/99e03e72e3f7e13506f80ef9ebaedccb929d84d0?narHash=sha256-AavrbMltJKcC2Fx0lfJoZfmy7g87ebXU0ddVenhajLA%3D' (2025-08-15)
• Updated input 'nixpkgs':
    'git+https://github.com/NixOS/nixpkgs?ref=nixos-unstable-small&rev=d4df8d6cc1ccfd3e4349a1d54e4fb1171e7ec1f5&shallow=1' (2025-08-13)
  → 'git+https://github.com/NixOS/nixpkgs?ref=nixos-unstable-small&rev=35f1742e4f1470817ff8203185e2ce0359947f12&shallow=1' (2025-08-16)

Author: github-actions[bot]