flake.lock: Update

Flake lock file updates:

• Updated input 'fenix':
    'github:nix-community/fenix/25db7a6f4de7dea678620785e03fbc4560c00672?narHash=sha256-wC9PR%2BrPjmcpnPdOIDwyNwQiRhNsuDs3oZY3t42f4uA%3D' (2025-07-26)
  → 'github:nix-community/fenix/bfa40349cb508ebec2a8d0f89d65022967d28dc4?narHash=sha256-xpbGgQ6ymKvz/LQ3RrUTHdbRKWznZAbdaNAH7TdbKZs%3D' (2025-09-20)
• Updated input 'fenix/rust-analyzer-src':
    'github:rust-lang/rust-analyzer/51e77c9d7b9b99f7a230bf5179ef1343befd71ac?narHash=sha256-5XbVpJwiy%2Bsw1v4PXSAz4lgJnVna6xkzqyZtoHymFJA%3D' (2025-07-25)
  → 'github:rust-lang/rust-analyzer/b12a1293473d4c1c74a63752184b8d21d32a6bde?narHash=sha256-PXDZtnSSNXIlTlytspxkTm/RENaQKdTJ44RGqm/LPLA%3D' (2025-09-19)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/6027c30c8e9810896b92429f0092f624f7b1aace?narHash=sha256-cnL5WWn/xkZoyH/03NNUS7QgW5vI7D1i74g48qplCvg%3D' (2025-07-25)
  → 'github:NixOS/nixpkgs/12bd230118a1901a4a5d393f9f56b6ad7e571d01?narHash=sha256-aBGl3XEOsjWw6W3AHiKibN7FeoG73dutQQEqnd/etR8%3D' (2025-09-19)

Author: github-actions[bot]