feat: update flake.lock (#93)

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/7fd36ee82c0275fb545775cc5e4d30542899511d?narHash=sha256-9h7%2B4/53cSfQ/uA3pSvCaBepmZaz/dLlLVJnbQ%2BSJjk%3D' (2025-07-25)
  → 'github:nixos/nixpkgs/94def634a20494ee057c76998843c015909d6311?narHash=sha256-K2ViRJfdVGE8tpJejs8Qpvvejks1%2BA4GQej/lBk5y7I%3D' (2025-07-31)

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Author: github-actions[bot]