Disable negative caching for local.hass.io (#202)

* Disable negative caching for local.hass.io

When a name under local.hass.io is queried before Supervisor's hosts
file entry is picked up (e.g. right after an add-on started), the
resulting NXDOMAIN is negative-cached for ~5s, prolonging resolution
failures even after the hosts entry became visible.

Disable caching of denial responses for local.hass.io. Positive answers
are still cached, and entries for these names live in the local hosts
file anyway, so negative caching provides no benefit here.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Apply negative caching exception to fallback corefile as well

The static /etc/corefile is used when tempio fails to render the
template; keep its cache block in sync.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: agners

rootfs/etc/corefile

@@ -21,7 +21,9 @@
         max_fails 5
     }
     fallback REFUSED,SERVFAIL,NXDOMAIN . dns://127.0.0.1:5553
-    cache
+    cache {
+        disable denial local.hass.io
+    }
 }
 
 .:5553 {

rootfs/usr/share/tempio/corefile

@@ -22,7 +22,9 @@
         max_fails 5
     }
     {{ if .fallback }}fallback REFUSED,SERVFAIL,NXDOMAIN . dns://127.0.0.1:5553{{ end }}
-    cache
+    cache {
+        disable denial local.hass.io
+    }
 }
 
 .:5553 {