fix(keel): resolve DNS lookup failures with k3s CoreDNS

Go's pure-Go DNS resolver has incompatibilities with k3s's CoreDNS that
cause intermittent "server misbehaving" errors after the initial lookup.
This prevented Keel from polling ghcr.io for new image digests.

Setting GODEBUG=netdns=cgo forces Go to use the system's cgo DNS resolver,
which works correctly with k3s.

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

infra/terraform/keel.tf

@@ -52,6 +52,19 @@ resource "helm_release" "keel" {
     value = "true"
   }
 
+  # Fix Go DNS resolver issues with k3s CoreDNS
+  # Go's pure-Go DNS resolver has trouble with k3s, so we force it to use
+  # the system (cgo) resolver instead
+  set {
+    name  = "extraEnv[0].name"
+    value = "GODEBUG"
+  }
+
+  set {
+    name  = "extraEnv[0].value"
+    value = "netdns=cgo"
+  }
+
   # Resource limits
   set {
     name  = "resources.requests.cpu"