build(nix): update dependencies

• Updated input 'fenix':
    'github:nix-community/fenix/0a6822c' (2026-01-16)
  → 'github:nix-community/fenix/8067797' (2026-01-18)
• Updated input 'fenix/nixpkgs':
    'github:nixos/nixpkgs/1412caf' (2026-01-13)
  → 'github:nixos/nixpkgs/e4bae1b' (2026-01-16)
• Updated input 'fenix/rust-analyzer-src':
    'github:rust-lang/rust-analyzer/adbff8b' (2026-01-15)
  → 'github:rust-lang/rust-analyzer/1cd5183' (2026-01-16)
• Updated input 'nixlib':
    'github:nix-community/nixpkgs.lib/a9f5b3b' (2026-01-11)
  → 'github:nix-community/nixpkgs.lib/78975aa' (2026-01-18)
• Updated input 'nixpkgs-unstable':
    'github:NixOS/nixpkgs/f4606b0' (2026-01-15)
  → 'github:NixOS/nixpkgs/3327b11' (2026-01-17)

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Author: github-actions[bot]