Initial commit: JMon cross-platform monitoring system

- gRPC client-server metrics collection
- PeriodicTimer-based 5-second sampling
- Delta encoding with configurable thresholds
- Queue/retry mechanism for resilience
- ProcessId tracking for duplicate detection
- Server-side state reconstruction
- Native AOT compilation support
- Docker/Podman containerization
- PostgreSQL + TimescaleDB persistence layer

JMonAgent/MetricsQueue.cs

@@ -0,0 +1,32 @@
+using System.Collections.Concurrent;
+
+namespace JMonAgent;
+
+public class MetricsQueue
+{
+    private readonly ConcurrentQueue<JMon.Protos.DeltaMetrics> _queue = new();
+    private readonly ILogger<MetricsQueue> _logger;
+
+    public MetricsQueue(ILogger<MetricsQueue> logger)
+    {
+        _logger = logger;
+    }
+
+    public void Enqueue(JMon.Protos.DeltaMetrics metrics)
+    {
+        _queue.Enqueue(metrics);
+        _logger.LogWarning("Metrics queued (total: {count})", _queue.Count);
+    }
+
+    public List<JMon.Protos.DeltaMetrics> DequeueAll()
+    {
+        var items = new List<JMon.Protos.DeltaMetrics>();
+        while (_queue.TryDequeue(out var item))
+        {
+            items.Add(item);
+        }
+        return items;
+    }
+
+    public int Count => _queue.Count;
+}