chore(deps): update flake.lock

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/bcd464c' (2026-04-01)
  → 'github:nixos/nixpkgs/54170c5' (2026-04-10)
• Updated input 'nixpkgs-unstable':
    'github:nixos/nixpkgs/6201e20' (2026-04-01)
  → 'github:nixos/nixpkgs/4c1018d' (2026-04-09)
• Updated input 'system-manager':
    'github:numtide/system-manager/7dced48' (2026-04-01)
  → 'github:numtide/system-manager/e131823' (2026-04-10)
• Updated input 'treefmt-nix':
    'github:numtide/treefmt-nix/7592596' (2026-04-02)
  → 'github:numtide/treefmt-nix/790751f' (2026-04-08)

Author: github-actions[bot]