Update flake.lock (#12750)

flake.lock: Update

Flake lock file updates:

• Updated input 'fenix':
    'github:nix-community/fenix/a050dbb' (2025-11-29)
  → 'github:nix-community/fenix/e8361cc' (2025-12-06)
• Updated input 'fenix/rust-analyzer-src':
    'github:rust-lang/rust-analyzer/36fa199' (2025-11-28)
  → 'github:rust-lang/rust-analyzer/2cbf358' (2025-12-05)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/59b6c96' (2025-11-29)
  → 'github:NixOS/nixpkgs/a672be6' (2025-12-05)

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]