feat: update flake.lock (#64)

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/6df24922a1400241dae323af55f30e4318a6ca65?narHash=sha256-dklw3AXr3OGO4/XT1Tu3Xz9n/we8GctZZ75ZWVqAVhk%3D' (2025-01-02)
  → 'github:nixos/nixpkgs/bffc22eb12172e6db3c5dde9e3e5628f8e3e7912?narHash=sha256-8YVQ9ZbSfuUk2bUf2KRj60NRraLPKPS0Q4QFTbc%2Bc2c%3D' (2025-01-08)

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Author: github-actions[bot]