fix preStart issue

default.nix

@@ -126,10 +126,6 @@ in
       wants = [ "network-online.target" ];
       wantedBy = [ "multi-user.target" ];
       
-      preStart = ''
-        # Ensure .env file exists with defaults if empty
-        if [ ! -s /var/lib/usda-vision/.env ]; then
-          if [ -f ${usda-vision-app}/opt/usda-vision/.env.example ]; then
       preStart = ''
         # Ensure .env file exists with defaults if empty
         if [ ! -s /var/lib/usda-vision/.env ]; then
@@ -139,7 +135,11 @@ in
             echo "Please edit /var/lib/usda-vision/.env with your configuration"
           fi
         fi
-      '';emainAfterExit = true;
+      '';
+
+      serviceConfig = {
+        Type = "oneshot";
+        RemainAfterExit = true;
         WorkingDirectory = "${usda-vision-app}/opt/usda-vision";
         User = "root";
         Group = "root";