chore: update flake.lock

Flake lock file updates:

• Updated input 'flake-parts':
    'github:hercules-ci/flake-parts/af66ad1' (2025-08-06)
  → 'github:hercules-ci/flake-parts/a34fae9' (2025-12-15)
• Updated input 'flake-parts/nixpkgs-lib':
    'github:nix-community/nixpkgs.lib/0f36c44' (2025-07-27)
  → 'github:nix-community/nixpkgs.lib/2075416' (2025-12-14)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/620f256' (2025-08-31)
  → 'github:NixOS/nixpkgs/a588fd0' (2026-01-04)
• Updated input 'pre-commit-hooks-nix':
    'github:cachix/pre-commit-hooks.nix/e891a93' (2025-08-23)
  → 'github:cachix/pre-commit-hooks.nix/f092770' (2026-01-01)
• Updated input 'pre-commit-hooks-nix/flake-compat':
    'github:edolstra/flake-compat/9100a0f' (2025-05-12)
  → 'github:NixOS/flake-compat/5edf11c' (2025-12-29)

Author: github-actions[bot]