flake.lock: Update (#878)

Flake lock file updates:

• Updated input 'neovim-nightly':
    'github:nix-community/neovim-nightly-overlay/da590e86c5019cc3a853f0003b44aef8950b5620?narHash=sha256-im6eWkpc8l8sRnv%2BuHcxGtUi4cE/rsete9Mo6GBpwqU%3D' (2026-04-11)
  → 'github:nix-community/neovim-nightly-overlay/f719e136a8e0cd91e70515e590385356abce1341?narHash=sha256-iJcGy0pW0wX7q6HAQuKx8sskTyu8an0l0gI3TBgzk3E%3D' (2026-04-12)
• Updated input 'neovim-nightly/neovim-src':
    'github:neovim/neovim/4f7b6083e5fe13ae0474520c769e1d3aeb25d393?narHash=sha256-mdxM2fMgNn7u2GEvaYJrtuYqM1ZYNHWevoqV/uGP6rE%3D' (2026-04-10)
  → 'github:neovim/neovim/4a289bfce3e71bf00d1eced168a6a7bbb270b95b?narHash=sha256-JXrr9lxKfTIm/VW4jvaB1RU9r%2B7pAoaXeDsy24TGPiw%3D' (2026-04-11)
• Updated input 'neovim-nightly/nixpkgs':
    'github:NixOS/nixpkgs/9d29d5f667d7467f98efc31881e824fa586c927e?narHash=sha256-omax7atcZbol%2B6HJ2RLpP%2BZCFcPa5bZ65Hn71RufeWQ%3D' (2026-04-10)
  → 'github:NixOS/nixpkgs/13043924aaa7375ce482ebe2494338e058282925?narHash=sha256-nwASzrRDD1JBEu/o8ekKYEXm/oJW6EMCzCRdrwcLe90%3D' (2026-04-11)
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/9d29d5f667d7467f98efc31881e824fa586c927e?narHash=sha256-omax7atcZbol%2B6HJ2RLpP%2BZCFcPa5bZ65Hn71RufeWQ%3D' (2026-04-10)
  → 'github:nixos/nixpkgs/13043924aaa7375ce482ebe2494338e058282925?narHash=sha256-nwASzrRDD1JBEu/o8ekKYEXm/oJW6EMCzCRdrwcLe90%3D' (2026-04-11)

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

Author: mrcjkb