fix: firefox gets wrong timezone on NixOS

Author: ryan4yin

modules/nixos/core-desktop.nix

@@ -1,4 +1,5 @@
 {
+  config,
   lib,
   pkgs,
   ...
@@ -209,4 +210,9 @@
       emoji = ["Noto Color Emoji"];
     };
   };
+
+  environment.variables = {
+    # fix https://github.com/NixOS/nixpkgs/issues/238025
+    TZ = "${config.time.timeZone}";
+  };
 }