flake.lock: Update (#401)

Flake lock file updates:

• Updated input 'home-manager':
    'github:nix-community/home-manager/bb35f07' (2025-12-19)
  → 'github:nix-community/home-manager/61fcc9d' (2025-12-21)
• Updated input 'nh':
    'github:nix-community/nh/0edf961' (2025-12-16)
  → 'github:nix-community/nh/84785ab' (2025-12-20)

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

Author: kclejeune