fix UI 503s under checkpoint load

- Store: skip identical CT checkpoint writes (CertSpotter calls StoreLogState
  per batch across 64 logs; hashing the state avoids redundant writes).
- webui: cache /api/stats for 10s and raise API query timeouts; UI polls, so
  repeated aggregate queries no longer queue behind checkpoint bursts.
- reword discovery detail (no 'name enumeration' for S3/GCS; only Azure uses a
  container list).

internal/discover/discover.go

@@ -231,7 +231,7 @@ func (d *Discoverer) scanAzure(ctx context.Context, account string) {
 		Provider: model.ProviderAzure, Service: model.ServiceBlobStorage,
 		ResourceSpecific: true, Source: model.SourceDiscovery,
 	}
-	d.cfg.OnOpen(ctx, c, "azure public container(s): "+strings.Join(found, ","), entries)
+	d.cfg.OnOpen(ctx, c, "azure anonymous listing allowed (container: "+strings.Join(found, ",")+")", entries)
 }
 
 // validAzureAccount mirrors Azure's naming rules: 3-24 lowercase alphanumerics.
@@ -299,7 +299,7 @@ func (d *Discoverer) test(ctx context.Context, t Target) {
 	if finalHost != "" && strings.HasSuffix(finalHost, ".amazonaws.com") {
 		c.Hostname = finalHost
 	}
-	detail := "discovered open bucket via name enumeration (" + t.Hostname + ")"
+	detail := "anonymous listing allowed"
 	if d.cfg.Metrics != nil {
 		d.cfg.Metrics.BucketOpen.Add(1)
 	}