flake.lock: Update

Flake lock file updates:

• Updated input 'emacs-overlay':
    'github:nix-community/emacs-overlay/370a91d' (2026-05-14)
  → 'github:nix-community/emacs-overlay/abaf50f' (2026-05-23)
• Updated input 'emacs-overlay/nixpkgs-stable':
    'github:NixOS/nixpkgs/8fd9daa' (2026-05-10)
  → 'github:NixOS/nixpkgs/687f05a' (2026-05-18)
• Updated input 'home-manager':
    'github:nix-community/home-manager/9846abe' (2026-05-15)
  → 'github:nix-community/home-manager/6e92bf0' (2026-05-24)
• Updated input 'nix-darwin':
    'github:LnL7/nix-darwin/8c62fba' (2026-05-03)
  → 'github:LnL7/nix-darwin/56c666e' (2026-05-17)
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/da5ad66' (2026-05-10)
  → 'github:nixos/nixpkgs/2991645' (2026-05-23)

Author: github-actions[bot]