ns/resolver: add redundant stub-zone addresses

Configure Unbound to query both ns1 and ns2 for the home.2rjus.net
zone, in addition to local NSD. This provides redundancy during
bootstrap or if local NSD is temporarily unavailable.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

services/ns/resolver.nix

@@ -45,7 +45,11 @@
       };
       stub-zone = {
         name = "home.2rjus.net";
-        stub-addr = "127.0.0.1@8053";
+        stub-addr = [
+          "127.0.0.1@8053"   # Local NSD
+          "10.69.13.5@8053"  # ns1
+          "10.69.13.6@8053"  # ns2
+        ];
       };
       forward-zone = {
         name = ".";