feat: use quad9 as the default DNS

hosts/battleship/configuration.nix

@@ -146,7 +146,7 @@
         prefixLength = 24;
       }
     ];
-    nameservers = ["8.8.8.8" "1.1.1.1"];
+    nameservers = ["9.9.9.9"];
   };
   hardware.pulseaudio.enable = false;
   security.rtkit.enable = true;

hosts/fighter/configuration.nix

@@ -126,7 +126,7 @@
         prefixLength = 24;
       }
     ];
-    nameservers = ["8.8.8.8" "1.1.1.1"];
+    nameservers = ["9.9.9.9"];
   };
 
   # Enable sound with pipewire.

hosts/spacestation/configuration.nix

@@ -60,6 +60,7 @@
         prefixLength = 24;
       }
     ];
+    nameservers = ["9.9.9.9"];
   };
 
   sound.enable = true;