Improve load balancing and move to pull based model

RemoteExec.Shared/ServerMetrics.cs

@@ -4,6 +4,7 @@ public sealed class ServerMetrics
 {
     public int ActiveConnections { get; set; }
     public int ActiveTasks { get; set; }
+    public int MaxConcurrentTasks { get; set; }
     public long TotalMemoryUsage { get; set; }
     public double CpuUsage { get; set; }
     public DateTime Timestamp { get; set; }

RemoteExec.Shared/TaskItem.cs

@@ -0,0 +1,7 @@
+namespace RemoteExec.Shared;
+
+public class TaskItem
+{
+    public Guid TaskId { get; set; }
+    public required RemoteExecutionRequest Request { get; set; }
+}