Eliminate hub-overrides.nix: write feature toggles into custom.nix instead

Agent-Logs-Url: https://github.com/naturallaw777/staging_alpha/sessions/db82f216-af3e-4d7f-a972-86c03f23e069

Co-authored-by: naturallaw777 <99053422+naturallaw777@users.noreply.github.com>

configuration.nix

@@ -4,9 +4,7 @@
   imports = [
     ./modules/modules.nix
     ./iso/branding.nix
-  ] ++ (if builtins.pathExists /etc/nixos/hub-overrides.nix
-        then [ /etc/nixos/hub-overrides.nix ]
-        else []);
+  ];
 
   # ── Boot ────────────────────────────────────────────────────
   boot.loader.systemd-boot.enable = true;