Fix ISO image filename configuration syntax

- Moved image.fileName to top-level (not under isoImage.image)
- Fixed syntax error that prevented ISO build

iso.nix

@@ -29,7 +29,6 @@
   # ISO-specific configuration
   isoImage = {
     # ISO image settings
-    image.fileName = "omnixy-${config.system.nixos.label}-${pkgs.stdenv.hostPlatform.system}.iso";
     volumeID = "OMNIXY_${lib.toUpper config.system.nixos.label}";
     
     # Boot configuration
@@ -69,6 +68,9 @@
   # Allow unfree packages
   nixpkgs.config.allowUnfree = true;
 
+  # ISO image filename
+  image.fileName = "omnixy-${config.system.nixos.label}-${pkgs.stdenv.hostPlatform.system}.iso";
+
   # Enable flakes
   nix = {
     settings = {