flake.lock: Update

Flake lock file updates:

• Updated input 'fenix':
    'github:nix-community/fenix/e917198' (2025-07-19)
  → 'github:nix-community/fenix/a050dbb' (2025-11-29)
• Updated input 'fenix/rust-analyzer-src':
    'github:rust-lang/rust-analyzer/330c4ed' (2025-07-18)
  → 'github:rust-lang/rust-analyzer/36fa199' (2025-11-28)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/6b49552' (2025-07-19)
  → 'github:NixOS/nixpkgs/59b6c96' (2025-11-29)

Author: github-actions[bot]