fix: add missing packages for zsh aliases and plugins

- home/pkg.nix: add eza, bat, ack, fzf
- modules/core/pkg.nix: add kubectl (for OMZ kubectl plugin)

home/pkg.nix

@@ -1,9 +1,16 @@
 { pkgs, ... }:
 {
-  home.packages = with pkgs;[
+  home.packages = with pkgs; [
+    # 文件/磁盘工具
     duf
     ncdu
     yazi
     fastfetch
+
+    # Shell 工具（zsh aliases 依赖）
+    eza          # ls/eza aliases
+    bat          # cat alias (bat -pp)
+    ack          # afind alias
+    fzf          # fzf-tab 依赖
   ];
 }

modules/core/pkg.nix

@@ -5,5 +5,8 @@
     git
     htop
     wget
+
+    # 系统级工具（多个 host 共用）
+    kubectl       # oh-my-zsh kubectl plugin
   ];
 }