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

modules/drivers/amdgpu.nix

@@ -3,14 +3,11 @@
   # Ryzen 7 9700X 核显（RDNA2）相关的用户态支持。
   # 作为辅助显卡配置保留；X 的主显卡驱动仍由
   # desktop profile / nvidia 模块控制。
+  # amdvlk 在 26.05 已被官方移除（AMD 弃用，RADV 默认启用）。
   hardware.graphics = {
     enable = true;
     extraPackages = with pkgs; [
-      amdvlk
       rocmPackages.clr.icd
     ];
-    extraPackages32 = with pkgs; [
-      driversi686Linux.amdvlk
-    ];
   };
 }