Add nixos/ directory with corrected modules

- kawa.nix: main module with fixed NATS options
- default.nix: default configuration
- kawa-base.nix: base module with NATS settings
- Hostname fixed (no /sys read)
- NATS: settings.http_port instead of httpPort

nixos/default.nix

@@ -1,18 +1,16 @@
 # KAWA OS - Configuration par défaut
-# Usage: import dans configuration.nix
+# Usage: imports = [ ./nixos ];
 
 { config, lib, pkgs, ... }:
 
 {
-  imports = [
-    ./kawa.nix
-  ];
+  imports = [ ./kawa.nix ];
   
   services.kawa = {
     enable = true;
+    hostname = "kawa-node"; # Fixe, pas de lecture /sys
     autoConnect = true;
-    enableNats = true;
+    enableOllama = false;
     enableSyncthing = true;
-    enableOllama = false; # Activer si GPU disponible
   };
 }