merge: observability (register rows 33, 54, 56, 63, 66) — LocalDb backlog KPI history + sustained-threshold badge, honest stream-subscriber gauge rename + real data-connection gauges, central metrics port on the rig, ASPNETCORE_ENVIRONMENT on site containers, import-session rejection counter

src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Monitoring/Health.razor

@@ -170,6 +170,17 @@
                                        IsAvailable="@_sfBufferDepthAvailable"
                                        ErrorMessage="@_sfBufferDepthError" />
                     </div>
+                    @* Register row 33. The point of charting the backlog is retrospective:
+                       the daily purge burst is expected, so what an operator needs is to see
+                       whether a past spike DRAINED — which a point-in-time tile can never
+                       answer. An unreplicated site emits no samples, so this chart is
+                       legitimately empty there rather than a flat, misleading zero line. *@
+                    <div class="col-lg-3 col-md-6">
+                        <KpiTrendChart Title="LocalDb Replication Backlog"
+                                       Points="@_localDbBacklogSeries"
+                                       IsAvailable="@_localDbBacklogAvailable"
+                                       ErrorMessage="@_localDbBacklogError" />
+                    </div>
                 </div>
             }
         </div>
@@ -248,6 +259,14 @@
                                     Metrics stale
                                 </span>
                             }
+                            @if (IsLocalDbBacklogSustained(state))
+                            {
+                                <span class="badge bg-warning text-dark"
+                                      data-test="localdb-backlog-badge"
+                                      title="LocalDb replication oplog backlog has stayed above @HealthOptions.Value.LocalDbBacklogThreshold for over @BacklogSustainedDisplay. A short daily spike at the site_events purge is expected and is NOT this — the peer has stopped draining.">
+                                    Replication backlog
+                                </span>
+                            }
                             @if (!state.IsOnline && state.LastStatusChangeAt is { } changedAt)
                             {
                                 <small class="text-muted">offline since @changedAt.ToString("u")</small>
@@ -526,6 +545,27 @@
     private string StaleTimeoutDisplay =>
         FormatDuration(HealthOptions.Value.MetricsStaleTimeout);
 
+    // Human-friendly rendering of the configured sustained-backlog dwell for the
+    // "Replication backlog" badge tooltip (e.g. "15 minutes").
+    private string BacklogSustainedDisplay =>
+        FormatDuration(HealthOptions.Value.LocalDbBacklogSustainedFor);
+
+    // Register row 33: the sustained LocalDb replication backlog badge.
+    //
+    // Reads the anchor the aggregator maintains (LocalDbBacklogAboveSince) rather than the
+    // instantaneous backlog on the report, because a bare "backlog > threshold" badge would
+    // fire on EVERY replicated site EVERY day: the site_events retention purge is CDC-captured
+    // like any other write, so the backlog jumps by the deleted batch size and then drains.
+    // Healthy is "the backlog comes back down"; only a dwell can express that.
+    //
+    // A site that reports no backlog at all (unreplicated — rig site-b/site-c — or a failed
+    // poll) never gets an anchor, so it can never be badged. That is the whole null-semantics
+    // requirement: null means "no reading", not zero.
+    private bool IsLocalDbBacklogSustained(SiteHealthState state) =>
+        state.IsOnline
+        && state.LocalDbBacklogAboveSince is { } since
+        && DateTimeOffset.UtcNow - since >= HealthOptions.Value.LocalDbBacklogSustainedFor;
+
     // Online central nodes, from the same ClusterNodes list the Nodes column renders.
     // Fewer than two means no standby, which disables the manual-failover control. This is
     // a display-side guard only — AkkaManualFailoverService re-checks against live cluster
@@ -616,6 +656,9 @@
     private IReadOnlyList<KpiSeriesPoint>? _sfBufferDepthSeries;
     private bool _sfBufferDepthAvailable = true;
     private string? _sfBufferDepthError;
+    private IReadOnlyList<KpiSeriesPoint>? _localDbBacklogSeries;
+    private bool _localDbBacklogAvailable = true;
+    private string? _localDbBacklogError;
 
     private static bool SiteHasActiveErrors(SiteHealthState state)
     {
@@ -739,6 +782,8 @@
                 await LoadTrendSeriesAsync(KpiMetrics.SiteHealth.ScriptErrors, siteId, fromUtc, toUtc);
             (_sfBufferDepthSeries, _sfBufferDepthAvailable, _sfBufferDepthError) =
                 await LoadTrendSeriesAsync(KpiMetrics.SiteHealth.SfBufferDepth, siteId, fromUtc, toUtc);
+            (_localDbBacklogSeries, _localDbBacklogAvailable, _localDbBacklogError) =
+                await LoadTrendSeriesAsync(KpiMetrics.SiteHealth.LocalDbOplogBacklog, siteId, fromUtc, toUtc);
         }
         finally
         {