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.

hosts/Garand-Desktop/printers.nix

@@ -1,14 +0,0 @@
-{
-  printEnable = false;
-
-  ensureDefaultPrinter = "Brother-T525W";
-
-  ensurePrinters = [
-    {
-      deviceUri = "ipp://192.168.1.110/ipp";
-      location = "home";
-      name = "Brother-T525W";
-      model = "everywhere";
-    }
-  ];
-}

hosts/Garand-Desktop/system-modules.nix

@@ -113,5 +113,6 @@ _: {
     gedit.enable = true; # Gedit: GNOME text editor
     winboat.enable = false; # Winboat: Windows remote desktop via RDP
     adb.enable = false; # ADB: Android SDK platform tools
+    simpleScan.enable = true; # simple-scan: Simple scanning utility
   };
 }

hosts/Garand-Desktop/variables.nix

@@ -62,4 +62,24 @@
   # Set network hostId if required (needed for zfs)
   # Otherwise leave as-is
   hostId = "5ab03f50";
+
+  # Whether printing services should be enabled.
+  printEnable = true;
+  # Name of the default printer.
+  ensureDefaultPrinter = "Brother_DCP-T510W";
+  # List of printers to ensure are configured.
+  ensurePrinters = [
+    {
+      deviceUri = "ipp://192.168.1.106/ipp";
+      location = "home";
+      name = "Brother_DCP-T525W";
+      model = "everywhere";
+    }
+    {
+      deviceUri = "ipp://192.168.1.159/ipp";
+      location = "home";
+      name = "Brother_DCP-T510W";
+      model = "everywhere";
+    }
+  ];
 }