flake.lock: Update

Flake lock file updates:

• Updated input 'fenix':
    'github:nix-community/fenix/b37f026b49ecb295a448c96bcbb0c174c14fc91b?narHash=sha256-icKFXb83uv2ezRCfuq5G8QSwCuaoLywLljSL%2BUGmPPI%3D' (2025-06-27)
  → 'github:nix-community/fenix/6ed03ef4c8ec36d193c18e06b9ecddde78fb7e42?narHash=sha256-tl/0cnsqB/Yt7DbaGMel2RLa7QG5elA8lkaOXli6VdY%3D' (2025-08-19)
• Updated input 'fenix/rust-analyzer-src':
    'github:rust-lang/rust-analyzer/317542c1e4a3ec3467d21d1c25f6a43b80d83e7d?narHash=sha256-hMNZXMtlhfjQdu1F4Fa/UFiMoXdZag4cider2R9a648%3D' (2025-06-25)
  → 'github:rust-lang/rust-analyzer/a905e3b21b144d77e1b304e49f3264f6f8d4db75?narHash=sha256-VX0B9hwhJypCGqncVVLC%2BSmeMVd/GAYbJZ0MiiUn2Pk%3D' (2025-08-18)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/7284e2decc982b81a296ab35aa46e804baaa1cfe?narHash=sha256-aVkL3/yu50oQzi2YuKo0ceiCypVZpZXYd2P2p1FMJM4%3D' (2025-06-25)
  → 'github:NixOS/nixpkgs/a58390ab6f1aa810eb8e0f0fc74230e7cc06de03?narHash=sha256-BA9MuPjBDx/WnpTJ0EGhStyfE7hug8g85Y3Ju9oTsM4%3D' (2025-08-19)

Author: sunng87