feat(nixos): refactor Git and GUI configuration handling

- Replaced `inherit` with explicit `settings` for Git user configuration.
- Unified Git configuration structure across NixOS and home modules.
- Adjusted GUI configuration by enabling `gdm.autoSuspend` and reordering options.

modules/home/tools/git/default.nix

@@ -31,13 +31,16 @@ in
     ];
     programs.git = {
       enable = true;
-      inherit (cfg) userName userEmail;
       lfs = enabled;
       signing = {
         key = cfg.signingKey;
         inherit (cfg) signByDefault;
       };
-      extraConfig = {
+      settings = {
+        user = {
+          email = cfg.userEmail;
+          name = cfg.userName;
+        };
         init = {
           defaultBranch = "main";
         };