Mark signed zones with a padlock, and name clients in statistics

The zones list shows a padlock after signed zones, linking to their
DNSSEC tab. Client lists in the statistics show the host name Jarl's
records have for each address (PTR, else A/AAAA); no DNS queries.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/stats/store.go

@@ -135,6 +135,9 @@ type topsWrite struct {
 type Entry struct {
 	Key   string `json:"key"`
 	Count int64  `json:"count"`
+	// Name is a client's host name, from Jarl's own records (set by the
+	// API for client lists).
+	Name string `json:"name,omitempty"`
 }
 
 // AddCounters adds values to the counters of a bucket.