flake.lock: Update

Flake lock file updates:

• Updated input 'home-manager':
    'github:nix-community/home-manager/e1fd735' (2026-05-12)
  → 'github:nix-community/home-manager/d1686dc' (2026-05-16)
• Updated input 'niri':
    'github:sodiboo/niri-flake/9ab3f8b' (2026-05-15)
  → 'github:sodiboo/niri-flake/daefca3' (2026-05-16)
• Updated input 'niri/nixpkgs':
    'github:NixOS/nixpkgs/da5ad66' (2026-05-10)
  → 'github:NixOS/nixpkgs/d233902' (2026-05-15)
• Updated input 'nixos-hardware':
    'github:NixOS/nixos-hardware/9bd7c80' (2026-05-12)
  → 'github:NixOS/nixos-hardware/379c1f2' (2026-05-16)
• Updated input 'nixpkgs-unstable':
    'github:nixos/nixpkgs/8a1b012' (2026-05-14)
  → 'github:nixos/nixpkgs/d233902' (2026-05-15)

Author: github-actions[bot]