flake.lock: Update (#1923)

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/73347dcecffada777f109886943fd3218266dde5?narHash=sha256-CA26lQJM1wM2//0ThWcp2ZeRqgcLfk892lEKRkypNbI%3D' (2025-08-23)
  → 'github:nixos/nixpkgs/45bbb3cb76ba73b1d288c4a9b8e4c8abff7aa48f?narHash=sha256-7NtfVRHAwFIDkHp0EopBDjgHpjoN/hy/Sn3ZmteaflY%3D' (2025-08-25)

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Author: github-actions[bot]