Clean up networking configuration structure

- Remove leftover networking.nix files from machine directories
- ZFS configuration moved to machine-specific configuration where it belongs
- Network module now contains only networking-related configuration
- Improved separation of concerns between network and machine configs

modules/network/network-congenital-optimist.nix

@@ -18,9 +18,4 @@
     ];
   };
 
-  # ZFS services for this machine
-  services.zfs = {
-    autoScrub.enable = true;
-    trim.enable = true;
-  };
 }