Disable syncthing discovery by default

syncthing/default.nix

@@ -1,9 +1,15 @@
-{ ... }:
+{ lib, ... }:
 {
   imports = [ ./folders ];
   services.syncthing = {
     enable = true;
     systemService = true;
     openDefaultPorts = true;
+    extraOptions = {
+      options = {
+        globalAnnounceEnabled = lib.mkDefault false;
+        localAnnounceEnabled = lib.mkDefault false;
+      };
+    };
   };
 }