chore: upgrade nixpkgs/home-manager to 26.05 and re-lock

- nixpkgs: nixos-25.05 -> nixos-26.05 (rev 70cc4559)
- home-manager: release-25.05 -> release-26.05
- fix 26.05 breaking changes: fcitx5-configtool/fcitx5-chinese-addons rename,
  resolved.extraConfig -> settings.Resolve, amdvlk removed (RADV default),
  desktop: import missing hardware-configuration.nix
- home/git.nix: migrate deprecated userName/extraConfig to settings

hosts/desktop/default.nix

@@ -2,5 +2,6 @@
 {
   imports = [
     ./configuration.nix
+    ./hardware-configuration.nix
   ];
 }