Add TaskSyncExtensions for sync Task execution (.NET FW)

Introduced TaskSyncExtensions class with Sync extension methods to allow synchronous execution of Task and Task<TResult> instances. This enables blocking on async code and is conditionally compiled for .NET Framework builds.

src/ReC.Client/TaskSyncExtensions.cs

@@ -0,0 +1,26 @@
+#if NETFRAMEWORK
+using System.Threading.Tasks;
+#endif
+
+namespace ReC.Client
+{
+    /// <summary>
+    /// Provides synchronous wrappers for Task-based operations.
+    /// </summary>
+    public static class TaskSyncExtensions
+    {
+        /// <summary>
+        /// Blocks until the task completes and propagates any exception.
+        /// </summary>
+        /// <param name="task">The task to wait for.</param>
+        public static void Sync(this Task task) => task.ConfigureAwait(false).GetAwaiter().GetResult();
+
+        /// <summary>
+        /// Blocks until the task completes and returns its result, propagating any exception.
+        /// </summary>
+        /// <typeparam name="TResult">The type of the task result.</typeparam>
+        /// <param name="task">The task to wait for.</param>
+        /// <returns>The result of the completed task.</returns>
+        public static TResult Sync<TResult>(this Task<TResult> task) => task.ConfigureAwait(false).GetAwaiter().GetResult();
+    }
+}