Phase 3 PR 27 — Fleet status dashboard page. New /fleet route shows per-node apply state (ClusterNodeGenerationState joined with ClusterNode for the ClusterId) in a sortable table with summary cards for Total / Applied / Stale / Failed node counts. Stale detection: LastSeenAt older than 30s triggers a table-warning row class + yellow count card. Failed rows get table-danger + red card. Badge classes per LastAppliedStatus: Applied=bg-success, Failed=bg-danger, Applying=bg-info, unknown=bg-secondary. Timestamps rendered as relative-age strings ('42s ago', '15m ago', '3h ago', then absolute date for >24h). Error column is truncated to 320px with the full message in a tooltip so the table stays readable on wide fleets. Initial data load on OnInitializedAsync; auto-refresh every 5s via a Timer that calls InvokeAsync(RefreshAsync) — matches the FleetStatusPoller's 5s cadence so the dashboard sees the most recent state without polling ahead of the broadcaster. A Refresh button also kicks a manual reload; _refreshing gate prevents double-runs when the timer fires during an in-flight query. IServiceScopeFactory (matches FleetStatusPoller's pattern) creates a fresh DI scope per refresh so the per-page DbContext can't race the timer with the render thread; no new DI registrations needed. Live SignalR hub push is deliberately deferred to a follow-up PR — the existing FleetStatusHub + NodeStateChangedMessage already works for external JavaScript clients; wiring an in-process Blazor Server consumer adds HubConnectionBuilder plumbing that's worth its own focused change. Sidebar link added to MainLayout between Overview and Clusters. Full Admin.Tests Unit suite 14 pass / 0 fail — unchanged, no tests regressed. Full Admin build clean (0 errors, 0 warnings). Closes the 'no per-driver dashboard' gap from lmx-followups item #7 at the fleet level; per-host (platform/engine/Modbus PLC) granularity still needs a dedicated page that consumes IHostConnectivityProbe.GetHostStatuses from the Server process — that's the live-SignalR follow-up.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ZB.MOM.WW.OtOpcUa.Admin/Components/Layout/MainLayout.razor

@@ -5,6 +5,7 @@
         <h5 class="mb-4">OtOpcUa Admin</h5>
         <ul class="nav flex-column">
             <li class="nav-item"><a class="nav-link text-light" href="/">Overview</a></li>
+            <li class="nav-item"><a class="nav-link text-light" href="/fleet">Fleet status</a></li>
             <li class="nav-item"><a class="nav-link text-light" href="/clusters">Clusters</a></li>
             <li class="nav-item"><a class="nav-link text-light" href="/reservations">Reservations</a></li>
         </ul>

src/ZB.MOM.WW.OtOpcUa.Admin/Components/Pages/Fleet.razor

@@ -0,0 +1,172 @@
+@page "/fleet"
+@using Microsoft.EntityFrameworkCore
+@using ZB.MOM.WW.OtOpcUa.Configuration
+@using ZB.MOM.WW.OtOpcUa.Configuration.Entities
+@inject IServiceScopeFactory ScopeFactory
+@implements IDisposable
+
+<h1 class="mb-4">Fleet status</h1>
+
+<div class="d-flex align-items-center mb-3 gap-2">
+    <button class="btn btn-sm btn-outline-primary" @onclick="RefreshAsync" disabled="@_refreshing">
+        @if (_refreshing) { <span class="spinner-border spinner-border-sm me-1" /> }
+        Refresh
+    </button>
+    <span class="text-muted small">
+        Auto-refresh every @RefreshIntervalSeconds s. Last updated: @(_lastRefreshUtc?.ToString("HH:mm:ss 'UTC'") ?? "—")
+    </span>
+</div>
+
+@if (_rows is null)
+{
+    <p>Loading…</p>
+}
+else if (_rows.Count == 0)
+{
+    <div class="alert alert-info">
+        No node state recorded yet. Nodes publish their state to the central DB on each poll; if
+        this list is empty, either no nodes have been registered or the poller hasn't run yet.
+    </div>
+}
+else
+{
+    <div class="row g-3 mb-4">
+        <div class="col-md-3">
+            <div class="card"><div class="card-body">
+                <h6 class="text-muted mb-1">Nodes</h6>
+                <div class="fs-3">@_rows.Count</div>
+            </div></div>
+        </div>
+        <div class="col-md-3">
+            <div class="card border-success"><div class="card-body">
+                <h6 class="text-muted mb-1">Applied</h6>
+                <div class="fs-3 text-success">@_rows.Count(r => r.Status == "Applied")</div>
+            </div></div>
+        </div>
+        <div class="col-md-3">
+            <div class="card border-warning"><div class="card-body">
+                <h6 class="text-muted mb-1">Stale</h6>
+                <div class="fs-3 text-warning">@_rows.Count(r => IsStale(r))</div>
+            </div></div>
+        </div>
+        <div class="col-md-3">
+            <div class="card border-danger"><div class="card-body">
+                <h6 class="text-muted mb-1">Failed</h6>
+                <div class="fs-3 text-danger">@_rows.Count(r => r.Status == "Failed")</div>
+            </div></div>
+        </div>
+    </div>
+
+    <table class="table table-hover align-middle">
+        <thead>
+            <tr>
+                <th>Node</th>
+                <th>Cluster</th>
+                <th>Generation</th>
+                <th>Status</th>
+                <th>Last applied</th>
+                <th>Last seen</th>
+                <th>Error</th>
+            </tr>
+        </thead>
+        <tbody>
+        @foreach (var r in _rows)
+        {
+            <tr class="@RowClass(r)">
+                <td><code>@r.NodeId</code></td>
+                <td>@r.ClusterId</td>
+                <td>@(r.GenerationId?.ToString() ?? "—")</td>
+                <td>
+                    <span class="badge @StatusBadge(r.Status)">@(r.Status ?? "—")</span>
+                </td>
+                <td>@FormatAge(r.AppliedAt)</td>
+                <td class="@(IsStale(r) ? "text-warning" : "")">@FormatAge(r.SeenAt)</td>
+                <td class="text-truncate" style="max-width: 320px;" title="@r.Error">@r.Error</td>
+            </tr>
+        }
+        </tbody>
+    </table>
+}
+
+@code {
+    // Refresh cadence. 5s matches FleetStatusPoller's poll interval — the dashboard always sees
+    // the most recent published state without polling ahead of the broadcaster.
+    private const int RefreshIntervalSeconds = 5;
+
+    private List<FleetNodeRow>? _rows;
+    private bool _refreshing;
+    private DateTime? _lastRefreshUtc;
+    private Timer? _timer;
+
+    protected override async Task OnInitializedAsync()
+    {
+        await RefreshAsync();
+        _timer = new Timer(async _ => await InvokeAsync(RefreshAsync),
+            state: null,
+            dueTime: TimeSpan.FromSeconds(RefreshIntervalSeconds),
+            period: TimeSpan.FromSeconds(RefreshIntervalSeconds));
+    }
+
+    private async Task RefreshAsync()
+    {
+        if (_refreshing) return;
+        _refreshing = true;
+        try
+        {
+            using var scope = ScopeFactory.CreateScope();
+            var db = scope.ServiceProvider.GetRequiredService<OtOpcUaConfigDbContext>();
+            var rows = await db.ClusterNodeGenerationStates.AsNoTracking()
+                .Join(db.ClusterNodes.AsNoTracking(), s => s.NodeId, n => n.NodeId, (s, n) => new FleetNodeRow(
+                    s.NodeId, n.ClusterId, s.CurrentGenerationId,
+                    s.LastAppliedStatus != null ? s.LastAppliedStatus.ToString() : null,
+                    s.LastAppliedError, s.LastAppliedAt, s.LastSeenAt))
+                .OrderBy(r => r.ClusterId)
+                .ThenBy(r => r.NodeId)
+                .ToListAsync();
+            _rows = rows;
+            _lastRefreshUtc = DateTime.UtcNow;
+        }
+        finally
+        {
+            _refreshing = false;
+            StateHasChanged();
+        }
+    }
+
+    private static bool IsStale(FleetNodeRow r)
+    {
+        if (r.SeenAt is null) return true;
+        return (DateTime.UtcNow - r.SeenAt.Value) > TimeSpan.FromSeconds(30);
+    }
+
+    private static string RowClass(FleetNodeRow r) => r.Status switch
+    {
+        "Failed" => "table-danger",
+        _ when IsStale(r) => "table-warning",
+        _ => "",
+    };
+
+    private static string StatusBadge(string? status) => status switch
+    {
+        "Applied" => "bg-success",
+        "Failed" => "bg-danger",
+        "Applying" => "bg-info",
+        _ => "bg-secondary",
+    };
+
+    private static string FormatAge(DateTime? t)
+    {
+        if (t is null) return "—";
+        var age = DateTime.UtcNow - t.Value;
+        if (age.TotalSeconds < 60) return $"{(int)age.TotalSeconds}s ago";
+        if (age.TotalMinutes < 60) return $"{(int)age.TotalMinutes}m ago";
+        if (age.TotalHours < 24) return $"{(int)age.TotalHours}h ago";
+        return t.Value.ToString("yyyy-MM-dd HH:mm 'UTC'");
+    }
+
+    public void Dispose() => _timer?.Dispose();
+
+    internal sealed record FleetNodeRow(
+        string NodeId, string ClusterId, long? GenerationId,
+        string? Status, string? Error, DateTime? AppliedAt, DateTime? SeenAt);
+}