fix(admin): use TLS-aware HTTP client for /dir/status fetch (#9227)

fetchPublicUrlMap() in weed/admin/dash/cluster_topology.go uses a
dedicated &http.Client{} that doesn't honor security.toml client TLS
configuration, and hardcodes "http://" in the URL. When master is
configured HTTPS-only ([https.master] set), every cluster topology
cache refresh logs:

  NOTICE: http: TLS handshake error from <admin-ip>:<port>: client
  sent an HTTP request to an HTTPS server

The function falls through to glog.V(1).Infof and returns nil, so the
admin UI loses PublicUrl enrichment for data nodes. Cosmetic but noisy.

Switch to util_http.GetGlobalHttpClient() whose Do() calls
NormalizeHttpScheme(), which automatically rewrites http:// to https://
when [https.client] is enabled and presents the configured client cert.
Preserve the 5-second timeout via context.WithTimeout().

Same pattern as weed/admin/handlers/file_browser_handlers.go,
weed/server/master_server.go, weed/shell/command_volume_fsck.go.

weed/admin/dash/cluster_topology.go

@@ -10,11 +10,10 @@ import (
 
 	"github.com/seaweedfs/seaweedfs/weed/glog"
 	"github.com/seaweedfs/seaweedfs/weed/pb/master_pb"
+	util_http "github.com/seaweedfs/seaweedfs/weed/util/http"
 )
 
-var dirStatusClient = &http.Client{
-	Timeout: 5 * time.Second,
-}
+const dirStatusTimeout = 5 * time.Second
 
 // GetClusterTopology returns the current cluster topology with caching
 func (s *AdminServer) GetClusterTopology() (*ClusterTopology, error) {
@@ -50,8 +49,16 @@ func (s *AdminServer) fetchPublicUrlMap() map[string]string {
 		return nil
 	}
 
+	ctx, cancel := context.WithTimeout(context.Background(), dirStatusTimeout)
+	defer cancel()
+
 	url := fmt.Sprintf("http://%s/dir/status", currentMaster.ToHttpAddress())
-	resp, err := dirStatusClient.Get(url)
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		glog.V(1).Infof("Failed to build /dir/status request for %s: %v", currentMaster, err)
+		return nil
+	}
+	resp, err := util_http.GetGlobalHttpClient().Do(req)
 	if err != nil {
 		glog.V(1).Infof("Failed to fetch /dir/status from %s: %v", currentMaster, err)
 		return nil