flake.lock: Update

Flake lock file updates:

• Updated input 'fenix':
    'github:nix-community/fenix/7d9ba794daf5e8cc7ee728859bc688d8e26d5f06' (2025-03-20)
  → 'github:nix-community/fenix/73f8c1fc7aeaf3bbdd59da1cb4bd94a57fc7d96d' (2025-09-21)
• Updated input 'fenix/rust-analyzer-src':
    'github:rust-lang/rust-analyzer/15d87419f1a123d8f888d608129c3ce3ff8f13d4' (2025-03-18)
  → 'github:rust-lang/rust-analyzer/187917fa5d494dbb844452decfdc90bfa81ccf45' (2025-09-20)
• Updated input 'flake-compat':
    'github:edolstra/flake-compat/ff81ac966bb2cae68946d5ed5fc4994f96d0ffec' (2024-12-04)
  → 'github:edolstra/flake-compat/9100a0f413b0c601e0533d1d94ffd501ce2e7885' (2025-05-12)
• Updated input 'flake-parts':
    'github:hercules-ci/flake-parts/f4330d22f1c5d2ba72d3d22df5597d123fdb60a9' (2025-03-07)
  → 'github:hercules-ci/flake-parts/4524271976b625a4a605beefd893f270620fd751' (2025-09-01)
• Updated input 'flake-parts/nixpkgs-lib':
    'github:nix-community/nixpkgs.lib/147dee35aab2193b174e4c0868bd80ead5ce755c' (2025-03-02)
  → 'github:nix-community/nixpkgs.lib/a73b9c743612e4244d865a2fdee11865283c04e6' (2025-08-10)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/63158b9cbb6ec93d26255871c447b0f01da81619' (2025-03-30)
  → 'github:NixOS/nixpkgs/51c8f9cfaae8306d135095bcdb3df9027f95542d' (2025-09-21)

Author: github-actions[bot]