build(nix): update dependencies

• Updated input 'fenix':
    'github:nix-community/fenix/81d6a75' (2026-01-20)
  → 'github:nix-community/fenix/b2344f3' (2026-01-31)
• Updated input 'fenix/nixpkgs':
    'github:nixos/nixpkgs/e4bae1b' (2026-01-16)
  → 'github:nixos/nixpkgs/bfc1b8a' (2026-01-26)
• Updated input 'fenix/rust-analyzer-src':
    'github:rust-lang/rust-analyzer/1b8952b' (2026-01-19)
  → 'github:rust-lang/rust-analyzer/eb05888' (2026-01-30)
• Updated input 'nixify':
    'github:rvolosatovs/nixify/66ce96c' (2025-12-19)
  → 'github:rvolosatovs/nixify/18f0d04' (2026-01-30)
• Updated input 'nixlib':
    'github:nix-community/nixpkgs.lib/78975aa' (2026-01-18)
  → 'github:nix-community/nixpkgs.lib/d4c8053' (2026-01-25)
• Updated input 'nixpkgs-unstable':
    'github:NixOS/nixpkgs/bde0902' (2026-01-19)
  → 'github:NixOS/nixpkgs/6308c3b' (2026-01-30)

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Author: github-actions[bot]