flake.lock: Update

Flake lock file updates:

• Updated input 'nixos-stable':
    'git+https://github.com/NixOS/nixpkgs?ref=nixos-25.05&rev=70c74b02eac46f4e4aa071e45a6189ce0f6d9265&shallow=1' (2025-06-06)
  → 'git+https://github.com/NixOS/nixpkgs?ref=nixos-25.05&rev=5b5be50345d4113d04ba58c444348849f5585b4a&shallow=1' (2025-10-01)
• Updated input 'nixos-unstable':
    'git+https://github.com/NixOS/nixpkgs?ref=nixpkgs-unstable&rev=08fcb0dcb59df0344652b38ea6326a2d8271baff&shallow=1' (2025-06-08)
  → 'git+https://github.com/NixOS/nixpkgs?ref=nixpkgs-unstable&rev=9547cfd27b5158eb612a6812dfc5c7b3d118b996&shallow=1' (2025-09-29)

Author: github-actions[bot]