flake.lock: Update (#418)

Flake lock file updates:

• Updated input 'home-manager':
    'github:nix-community/home-manager/7ba4ee4' (2026-04-08)
  → 'github:nix-community/home-manager/e35c39f' (2026-04-10)
• Updated input 'nixos-unstable':
    'github:nixos/nixpkgs/68d8aa3' (2026-04-05)
  → 'github:nixos/nixpkgs/4c1018d' (2026-04-09)
• Updated input 'unstable':
    'github:nixos/nixpkgs/456e8a9' (2026-04-08)
  → 'github:nixos/nixpkgs/b018897' (2026-04-09)

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

Author: kclejeune