feat(health): wire up NodeHostname, ConnectionEndpoint, TagQuality, ParkedMessageCount collectors

- AkkaHostedService: SetNodeHostname from NodeOptions
- DataConnectionActor: UpdateConnectionEndpoint on state transitions,
  track per-tag quality counts and UpdateTagQuality on value changes
- HealthReportSender: query StoreAndForwardStorage for parked message count
- StoreAndForwardStorage: add GetParkedMessageCountAsync()

src/ScadaLink.DataConnectionLayer/Actors/DataConnectionActor.cs

@@ -66,6 +66,11 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
     private int _totalSubscribed;
     private int _resolvedTags;
 
+    private int _tagsGoodQuality;
+    private int _tagsBadQuality;
+    private int _tagsUncertainQuality;
+    private readonly Dictionary<string, QualityCode> _lastTagQuality = new();
+
     private IDictionary<string, string> _connectionDetails;
     private readonly IDictionary<string, string> _primaryConfig;
     private readonly IDictionary<string, string>? _backupConfig;
@@ -144,6 +149,7 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
     {
         _log.Info("[{0}] Entering Connecting state", _connectionName);
         _healthCollector.UpdateConnectionHealth(_connectionName, ConnectionHealth.Connecting);
+        _healthCollector.UpdateConnectionEndpoint(_connectionName, "Connecting");
         Become(Connecting);
         Self.Tell(new AttemptConnect());
     }
@@ -179,6 +185,8 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
         _log.Info("[{0}] Entering Connected state", _connectionName);
         _healthCollector.UpdateConnectionHealth(_connectionName, ConnectionHealth.Connected);
         _healthCollector.UpdateTagResolution(_connectionName, _totalSubscribed, _resolvedTags);
+        var endpointLabel = _backupConfig == null ? "Connected" : $"Connected to {_activeEndpoint.ToString().ToLower()}";
+        _healthCollector.UpdateConnectionEndpoint(_connectionName, endpointLabel);
         Become(Connected);
         Stash.UnstashAll();
     }
@@ -226,6 +234,7 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
     {
         _log.Warning("[{0}] Entering Reconnecting state", _connectionName);
         _healthCollector.UpdateConnectionHealth(_connectionName, ConnectionHealth.Disconnected);
+        _healthCollector.UpdateConnectionEndpoint(_connectionName, "Disconnected");
         Become(Reconnecting);
 
         // WP-9: Push bad quality for all subscribed tags on disconnect
@@ -552,6 +561,14 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
 
             subscriber.Tell(new ConnectionQualityChanged(_connectionName, QualityCode.Bad, now));
         }
+
+        // All tags now bad quality
+        _tagsGoodQuality = 0;
+        _tagsUncertainQuality = 0;
+        _tagsBadQuality = _lastTagQuality.Count;
+        foreach (var key in _lastTagQuality.Keys.ToList())
+            _lastTagQuality[key] = QualityCode.Bad;
+        _healthCollector.UpdateTagQuality(_connectionName, _tagsGoodQuality, _tagsBadQuality, _tagsUncertainQuality);
     }
 
     // ── Re-subscribe (WP-10) ──
@@ -646,6 +663,27 @@ public class DataConnectionActor : UntypedActor, IWithStash, IWithTimers
                     _connectionName, msg.TagPath, msg.Value.Value, msg.Value.Quality, msg.Value.Timestamp));
             }
         }
+
+        // Track quality transitions
+        if (_lastTagQuality.TryGetValue(msg.TagPath, out var prevQuality))
+        {
+            // Decrement old quality bucket
+            switch (prevQuality)
+            {
+                case QualityCode.Good: _tagsGoodQuality--; break;
+                case QualityCode.Bad: _tagsBadQuality--; break;
+                case QualityCode.Uncertain: _tagsUncertainQuality--; break;
+            }
+        }
+        // Increment new quality bucket
+        switch (msg.Value.Quality)
+        {
+            case QualityCode.Good: _tagsGoodQuality++; break;
+            case QualityCode.Bad: _tagsBadQuality++; break;
+            case QualityCode.Uncertain: _tagsUncertainQuality++; break;
+        }
+        _lastTagQuality[msg.TagPath] = msg.Value.Quality;
+        _healthCollector.UpdateTagQuality(_connectionName, _tagsGoodQuality, _tagsBadQuality, _tagsUncertainQuality);
     }
 
     // ── Internal messages ──

src/ScadaLink.HealthMonitoring/HealthReportSender.cs

@@ -2,6 +2,7 @@ using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 using ScadaLink.Commons.Messages.Health;
+using ScadaLink.StoreAndForward;
 
 namespace ScadaLink.HealthMonitoring;
 
@@ -16,6 +17,7 @@ public class HealthReportSender : BackgroundService
     private readonly HealthMonitoringOptions _options;
     private readonly ILogger<HealthReportSender> _logger;
     private readonly string _siteId;
+    private readonly StoreAndForwardStorage? _sfStorage;
     private long _sequenceNumber;
 
     public HealthReportSender(
@@ -23,13 +25,15 @@ public class HealthReportSender : BackgroundService
         IHealthReportTransport transport,
         IOptions<HealthMonitoringOptions> options,
         ILogger<HealthReportSender> logger,
-        ISiteIdentityProvider siteIdentityProvider)
+        ISiteIdentityProvider siteIdentityProvider,
+        StoreAndForwardStorage? sfStorage = null)
     {
         _collector = collector;
         _transport = transport;
         _options = options.Value;
         _logger = logger;
         _siteId = siteIdentityProvider.SiteId;
+        _sfStorage = sfStorage;
     }
 
     /// <summary>
@@ -54,6 +58,16 @@ public class HealthReportSender : BackgroundService
                 if (!_collector.IsActiveNode)
                     continue;
 
+                if (_sfStorage != null)
+                {
+                    try
+                    {
+                        var parkedCount = await _sfStorage.GetParkedMessageCountAsync();
+                        _collector.SetParkedMessageCount(parkedCount);
+                    }
+                    catch { /* Non-fatal — parked count will be 0 */ }
+                }
+
                 var seq = Interlocked.Increment(ref _sequenceNumber);
                 var report = _collector.CollectReport(_siteId);
 

src/ScadaLink.HealthMonitoring/ScadaLink.HealthMonitoring.csproj

@@ -16,6 +16,7 @@
 
   <ItemGroup>
     <ProjectReference Include="../ScadaLink.Commons/ScadaLink.Commons.csproj" />
+    <ProjectReference Include="../ScadaLink.StoreAndForward/ScadaLink.StoreAndForward.csproj" />
   </ItemGroup>
 
   <ItemGroup>

src/ScadaLink.Host/Actors/AkkaHostedService.cs

@@ -241,6 +241,7 @@ akka {{
 
         // Resolve the health collector for the Deployment Manager
         var siteHealthCollector = _serviceProvider.GetService<ScadaLink.HealthMonitoring.ISiteHealthCollector>();
+        siteHealthCollector?.SetNodeHostname(_nodeOptions.NodeHostname);
 
         // Create SiteReplicationActor on every node (not a singleton)
         var sfStorage = _serviceProvider.GetRequiredService<StoreAndForwardStorage>();

src/ScadaLink.StoreAndForward/StoreAndForwardStorage.cs

@@ -297,6 +297,20 @@ public class StoreAndForwardStorage
         return messages.FirstOrDefault();
     }
 
+    /// <summary>
+    /// Gets the count of parked messages (for health reporting).
+    /// </summary>
+    public async Task<int> GetParkedMessageCountAsync()
+    {
+        await using var conn = new SqliteConnection(_connectionString);
+        await conn.OpenAsync();
+        await using var cmd = conn.CreateCommand();
+        cmd.CommandText = "SELECT COUNT(*) FROM sf_messages WHERE status = @parked";
+        cmd.Parameters.AddWithValue("@parked", (int)StoreAndForwardMessageStatus.Parked);
+        var result = await cmd.ExecuteScalarAsync();
+        return Convert.ToInt32(result);
+    }
+
     /// <summary>
     /// Gets total message count by status.
     /// </summary>