refactor(nixos): standardize configuration structures

- Renamed and reorganized configuration keys for consistency (`settings` usage).
- Updated Postfix, systemd, and Syncthing configurations to adhere to the standardized format.
- Improved maintainability and readability of NixOS configurations.

systems/x86_64-linux/sgx/default.nix

@@ -64,7 +64,7 @@
   systemd.targets.hybrid-sleep.enable = false;
   services.xserver.displayManager.gdm.autoSuspend = false;
 
-  services.logind.lidSwitch = "ignore";
+  services.logind.settings.Login.HandleLidSwitch = "ignore";
 
   system.stateVersion = "23.11";
 }

systems/x86_64-linux/sgx/fileserver.nix

@@ -117,7 +117,8 @@
     dataDir = "/mnt/raid/Qmultimedia/syncthing"; # Default folder for new synced folders
     configDir = "/mnt/raid/Qmultimedia/syncthing/.config/syncthing"; # Folder for Syncthing's settings and keys
     guiAddress = "127.0.0.1:8384";
-    settings.gui.insecureSkipHostcheck = true;
+    settings = {
+      gui.insecureSkipHostcheck = true;
       devices = {
         "sgx" = {
           id = "2AAVSVQ-PK66I2B-2B4KWAU-TF674DG-IXNEKLF-CIWK7HG-7MUC7OW-DQQNAQM";
@@ -151,4 +152,5 @@
         };
       };
     };
+  };
 }

systems/x86_64-linux/sgx/mail.nix

@@ -7,8 +7,8 @@
 
   services.postfix = {
     enable = true;
-    settings.main.relayhost = [ "[smtp.gmail.com]:587" ];
-    config = {
+    setting.main = {
+      relayhost = [ "[smtp.gmail.com]:587" ];
       smtp_use_tls = "yes";
       smtp_sasl_auth_enable = "yes";
       smtp_sasl_security_options = "";