Add health check endpoints for telemetry

Introduces HTTP health check endpoints for monitoring node status:

- /health: Combined health status with JSON response
- /health/live: Kubernetes liveness probe endpoint
- /health/ready: Kubernetes readiness probe endpoint

Features:
- Configurable health port (defaults to Prometheus port)
- Sync status check based on block height comparison
- Memory pressure detection
- Peer connectivity validation
- JSON response with detailed health information

Author: Jim8y

src/Plugins/Telemetry/Health/HealthCheckEndpoint.cs

@@ -123,13 +123,16 @@ private JObject GetHealthStatus()
                 var headerHeight = _system.HeaderCache.Last?.Index ?? currentHeight;
                 var blocksBehind = headerHeight - currentHeight;
                 var isSynced = blocksBehind <= 2;
-                var peerCount = 0;
+
+                // Get actual peer count from LocalNode
+                var peerCount = _system.LocalNode.Ask<int>(new Network.P2P.LocalNode.GetConnectedCount()).Result;
+                var hasPeers = peerCount > 0;
 
                 var memPool = _system.MemPool;
                 var mempoolCount = memPool.Count;
                 var mempoolCapacity = memPool.Capacity;
 
-                var status = isSynced && peerCount >= 0 ? "healthy" : "degraded";
+                var status = isSynced && hasPeers ? "healthy" : "degraded";
 
                 return new JObject
                 {
@@ -147,6 +150,11 @@ private JObject GetHealthStatus()
                             ["blocks_behind"] = blocksBehind,
                             ["synced"] = isSynced
                         },
+                        ["network"] = new JObject
+                        {
+                            ["status"] = hasPeers ? "healthy" : "degraded",
+                            ["peer_count"] = peerCount
+                        },
                         ["mempool"] = new JObject
                         {
                             ["status"] = "healthy",

src/Plugins/Telemetry/Telemetry.cs

@@ -10,6 +10,7 @@
 // modifications are permitted.
 
 using Neo.Plugins.Telemetry.Collectors;
+using Neo.Plugins.Telemetry.Health;
 using Prometheus;
 using System.Timers;
 using Timer = System.Timers.Timer;
@@ -27,6 +28,7 @@ public class Telemetry : Plugin
 
         private NeoSystem? _system;
         private MetricServer? _metricServer;
+        private HealthCheckEndpoint? _healthEndpoint;
         private Timer? _collectionTimer;
 
         // Collectors
@@ -39,6 +41,7 @@ public class Telemetry : Plugin
         private bool _isRunning;
         private readonly object _collectionLock = new();
         private bool _isCollecting;
+        private string _networkName = "unknown";
 
         public Telemetry()
         {
@@ -66,17 +69,20 @@ protected internal override void OnSystemLoaded(NeoSystem system)
             try
             {
                 // Determine network name from protocol settings
-                var networkName = DetermineNetworkName(system);
+                _networkName = DetermineNetworkName(system);
                 var nodeId = TelemetrySettings.Default.NodeId;
 
-                Log($"Starting telemetry collection for node '{nodeId}' on network '{networkName}'", LogLevel.Info);
+                Log($"Starting telemetry collection for node '{nodeId}' on network '{_networkName}'", LogLevel.Info);
 
                 // Initialize collectors based on configuration
-                InitializeCollectors(system, nodeId, networkName);
+                InitializeCollectors(system, nodeId, _networkName);
 
                 // Start Prometheus metric server
                 StartMetricServer();
 
+                // Start health endpoint
+                StartHealthEndpoint();
+
                 // Start periodic collection timer
                 StartCollectionTimer();
 
@@ -180,6 +186,24 @@ private void StartCollectionTimer()
             Log($"Metrics collection timer started with interval {intervalMs}ms", LogLevel.Debug);
         }
 
+        private void StartHealthEndpoint()
+        {
+            var settings = TelemetrySettings.Default;
+
+            try
+            {
+                var host = settings.PrometheusHost;
+                var port = settings.HealthPort ?? settings.PrometheusPort;
+
+                _healthEndpoint = new HealthCheckEndpoint(_system!, host, port, settings.NodeId, _networkName);
+                Log($"Health endpoints started at http://{host}:{port}/health", LogLevel.Info);
+            }
+            catch (Exception ex)
+            {
+                Log($"Failed to start health endpoint: {ex.Message}", LogLevel.Warning);
+            }
+        }
+
         private void OnCollectionTimerElapsed(object? sender, ElapsedEventArgs e)
         {
             if (!_isRunning) return;
@@ -260,6 +284,8 @@ private void StopTelemetry()
                 _mempoolCollector = null;
                 _systemCollector = null;
                 _pluginCollector = null;
+                _healthEndpoint?.Dispose();
+                _healthEndpoint = null;
 
                 Log("Telemetry plugin shut down successfully", LogLevel.Info);
             }