feat(oksys): finish pihole config

devices/oksys/modules/pihole.nix

@@ -4,7 +4,7 @@
   services.pihole = {
     enable = true;
 
-    dnsPort = 5353;
+    dnsPort = 53;
     webPort = 8080;
 
     piholeConfig = {
@@ -22,6 +22,13 @@
         password = "password";
       };
 
+      # Declaratively set the DNS settings
+      # in Settings -> DNS -> Interface settings
+      dnsmasq.extraConfig = ''
+        interface=tailscale0
+        except-interface=nonexisting
+      '';
+
       # Handle it with unbound
       dns.upstreamServers = [
         "127.0.0.1#5335"