flake.lock: Update

Flake lock file updates:

• Updated input 'home-manager':
    'github:nix-community/home-manager/8a423e4' (2026-04-14)
  → 'github:nix-community/home-manager/d401492' (2026-04-16)
• Updated input 'nh':
    'github:nix-community/nh/d1861b2' (2026-04-13)
  → 'github:nix-community/nh/1341576' (2026-04-15)
• Updated input 'nixos-unstable':
    'github:nixos/nixpkgs/4c1018d' (2026-04-09)
  → 'github:nixos/nixpkgs/4bd9165' (2026-04-14)
• Updated input 'stable':
    'github:nixos/nixpkgs/7e495b7' (2026-04-13)
  → 'github:nixos/nixpkgs/1766437' (2026-04-15)
• Updated input 'unstable':
    'github:nixos/nixpkgs/1304392' (2026-04-11)
  → 'github:nixos/nixpkgs/566acc0' (2026-04-15)

Author: github-actions[bot]