feat: redesign the project structure

modules/nixos/gui-apps.nix

@@ -0,0 +1,17 @@
+{ config, pkgs, ... }:
+
+{
+  # this params has problem with home-manager,
+  # so defined as NixOS Module here.
+  nixpkgs.config.permittedInsecurePackages = [
+    "electron-19.0.7"  # required by wechat-uos, and it's already EOL
+    "openssl-1.1.1t"   # OpenSSL 1.1 is reaching its end of life on 2023/09/11
+  ];
+
+  environment.systemPackages = with config.nur.repos.xddxdd; [
+    # packages from nur-xddxdd
+    wechat-uos
+  ];
+
+  # flatpack is recommended to install other apps such as netease-cloud-music/qqmusic/...
+}