chore(deps): update nix flake.lock (#25)

Automated changes by the
[update-flake-lock](https://github.com/DeterminateSystems/update-flake-lock)
GitHub Action.

```
Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/7df7ff7d8e00218376575f0acdcc5d66741351ee?narHash=sha256-gTrEEp5gEspIcCOx9PD8kMaF1iEmfBcTbO0Jag2QhQs%3D' (2025-10-02)
  → 'github:NixOS/nixpkgs/0b4defa2584313f3b781240b29d61f6f9f7e0df3?narHash=sha256-Oncbh0UmHjSlxO7ErQDM3KM0A5/Znfofj2BSzlHLeVw%3D' (2025-10-09)
```

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