flake.lock: Update

Flake lock file updates:

• Updated input 'determinate-nixd-aarch64-darwin':
    'https://install.determinate.systems/determinate-nixd/tag/v3.15.0/macOS'
  → 'https://install.determinate.systems/determinate-nixd/tag/v3.15.1/macOS'
• Updated input 'determinate-nixd-aarch64-linux':
    'https://install.determinate.systems/determinate-nixd/tag/v3.15.0/aarch64-linux'
  → 'https://install.determinate.systems/determinate-nixd/tag/v3.15.1/aarch64-linux'
• Updated input 'determinate-nixd-x86_64-linux':
    'https://install.determinate.systems/determinate-nixd/tag/v3.15.0/x86_64-linux'
  → 'https://install.determinate.systems/determinate-nixd/tag/v3.15.1/x86_64-linux'
• Updated input 'nix':
    'https://api.flakehub.com/f/pinned/DeterminateSystems/nix-src/3.15.0/019b3854-cca6-7298-a91c-0fd8551a7270/source.tar.gz' (2025-12-19)
  → 'https://api.flakehub.com/f/pinned/DeterminateSystems/nix-src/3.15.1/019b4e84-d036-75db-b6c6-6bc2e2035c53/source.tar.gz' (2025-12-24)
• Updated input 'nixpkgs':
    'https://api.flakehub.com/f/pinned/DeterminateSystems/nixpkgs-weekly/0.1.911985%2Brev-09b8fda8959d761445f12b55f380d90375a1d6bb/019b25ab-7c11-79e0-a0b0-c94d455b7190/source.tar.gz' (2025-12-15)
  → 'https://api.flakehub.com/f/pinned/DeterminateSystems/nixpkgs-weekly/0.1.914780%2Brev-306ea70f9eb0fb4e040f8540e2deab32ed7e2055/019b49b8-ed0f-724e-bdaf-5fd90cc1c590/source.tar.gz' (2025-12-21)

Author: github-actions[bot]