flake.lock: Update

Flake lock file updates:

• Updated input 'home-manager':
    'github:nix-community/home-manager/b179bde' (2026-05-25)
  → 'github:nix-community/home-manager/e28654b' (2026-06-02)
• Updated input 'niri':
    'github:sodiboo/niri-flake/3cb351d' (2026-05-29)
  → 'github:sodiboo/niri-flake/134a4f0' (2026-06-01)
• Updated input 'niri/nixpkgs':
    'github:NixOS/nixpkgs/64c08a7' (2026-05-23)
  → 'github:NixOS/nixpkgs/331800d' (2026-05-31)
• Updated input 'nixos-hardware':
    'github:NixOS/nixos-hardware/b76b563' (2026-05-29)
  → 'github:NixOS/nixos-hardware/4ed851c' (2026-06-01)
• Updated input 'nixpkgs-unstable':
    'github:nixos/nixpkgs/e9a7635' (2026-05-29)
  → 'github:nixos/nixpkgs/3109eaa' (2026-05-31)

Author: github-actions[bot]