flake.lock: Update (#885)

Flake lock file updates:

• Updated input 'devenv':
    'github:cachix/devenv/23120f1' (2026-05-08)
  → 'github:cachix/devenv/768261d' (2026-05-16)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/0c88e1f' (2026-05-05)
  → 'github:NixOS/nixpkgs/d7a713c' (2026-05-14)

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

Author: brianmay-actions