fix: include hostname hints in metadata for API-side fallback

Send all available hostname sources (ComputerName, LocalHostName,
HostName, os.Hostname) in the metadata map when provisioning.
This allows the API to detect and repair generic hostnames like
'Mac' by picking the best available source server-side.

Belt and suspenders: preferredHostname() picks the right one
client-side, but metadata gives the API a second chance.

internal/controld/config.go

@@ -133,6 +133,15 @@ func FetchResolverUID(ctx context.Context, req *UtilityOrgRequest, version strin
 		ctrld.Log(ctx, logger.Debug(), "Using provided hostname: %s", hostname)
 	}
 
+	// Include all hostname sources in metadata so the API can pick the
+	// best one if the primary looks generic (e.g., "Mac", "Mac.lan").
+	if req.Metadata == nil {
+		req.Metadata = make(map[string]string)
+	}
+	for k, v := range hostnameHints() {
+		req.Metadata["hostname_"+k] = v
+	}
+
 	ctrld.Log(ctx, logger.Debug(), "Sending UID request to ControlD API")
 	body, _ := json.Marshal(req)
 	return postUtilityAPI(ctx, version, cdDev, false, bytes.NewReader(body))