Consolidate printer config and enable simple-scan

Remove per‑host printers.nix and merge printing settings into host
variables.
Add simple-scan package and enable it for desktop and laptop hosts.
Disable simple-scan for the default host.
Enable SANE daemon and expose its libraries in fish init.
Open required UDP ports 5353 and 54925 in network module.

modules/core/network.nix

@@ -34,6 +34,8 @@
         }
       ];
       allowedUDPPorts = [
+        5353
+        54925
         59010
         59011
       ];

modules/core/packages/packages.nix

@@ -76,6 +76,7 @@
     notify = notify-client;
     boxes = gnome-boxes;
     switcheroo = switcheroo;
+    simpleScan = simple-scan;
   };
 in {
   imports = builtins.attrValues (builtins.mapAttrs mkPackage packages);

modules/core/printing.nix

@@ -31,8 +31,12 @@
     ipp-usb.enable = true;
   };
 
-  hardware.printers = lib.mkIf printEnable {
-    ensureDefaultPrinter = ensureDefaultPrinter;
-    ensurePrinters = ensurePrinters;
+  hardware = lib.mkIf printEnable {
+    printers = {
+      ensureDefaultPrinter = ensureDefaultPrinter;
+      ensurePrinters = ensurePrinters;
+    };
+
+    sane.enable = true;
   };
 }