Remove Pear, use Jupiter as school device, generalize extra users

hosts/kitty/default.nix

@@ -6,7 +6,7 @@
     ./filesystems
     ./hardware
     ./network
-    ./users
+    ./user
     ../../modules/system
   ];
 
@@ -17,6 +17,7 @@
 
   system = {
     server.enable = true;
+    extraUsers.enable = true;
     stateVersion = "24.11";
   };