Add tests for GetDynamicAsync method in RecActionApiTests

Added a `using` directive for `System.Text.Json` to support JSON
operations. Introduced two new test methods:
`GetDynamicAsync_without_filters_returns_dynamic_payload_or_throws_not_found`
to validate the behavior of `GetDynamicAsync` without filters, and
`GetDynamicAsync_with_unknown_profile_throws_not_found` to ensure
proper handling of unknown profile IDs.

tests/ReC.Tests/Client/RecActionApiTests.cs

@@ -1,4 +1,5 @@
 using System.Net;
+using System.Text.Json;
 using Microsoft.Extensions.Configuration;
 using ReC.Application.Common.Dto;
 using ReC.Application.Common.Procedures.UpdateProcedure.Dto;
@@ -41,6 +42,27 @@ public class RecActionApiTests : RecClientTestBase
         }
     }
 
+    [Test]
+    public async Task GetDynamicAsync_without_filters_returns_dynamic_payload_or_throws_not_found()
+    {
+        var (client, scope) = CreateScopedClient();
+        using var _ = scope;
+
+        try
+        {
+            dynamic? actions = await client.RecActions.GetDynamicAsync();
+            Assert.That(actions, Is.Not.Null);
+            Assert.That(actions, Is.TypeOf<JsonElement>());
+            Assert.That(((JsonElement)actions).ValueKind, Is.EqualTo(JsonValueKind.Array));
+        }
+        catch (ReCApiException ex)
+        {
+            Assert.That(ex.StatusCode, Is.EqualTo(HttpStatusCode.NotFound));
+            Assert.That(ex.Method, Is.EqualTo("GET"));
+            Assert.That(ex.RequestUri!.AbsolutePath, Does.EndWith("api/RecAction"));
+        }
+    }
+
     [Test]
     public async Task GetAsync_with_profile_filter_returns_only_matching_actions()
     {
@@ -81,6 +103,21 @@ public class RecActionApiTests : RecClientTestBase
         Assert.That(ex.RequestUri!.Query, Does.Contain("ProfileId="));
     }
 
+    [Test]
+    public void GetDynamicAsync_with_unknown_profile_throws_not_found()
+    {
+        var (client, scope) = CreateScopedClient();
+        using var _ = scope;
+
+        var ex = Assert.ThrowsAsync<ReCApiException>(async () =>
+            await client.RecActions.GetDynamicAsync(profileId: long.MaxValue));
+
+        Assert.That(ex, Is.Not.Null);
+        Assert.That(ex!.StatusCode, Is.EqualTo(HttpStatusCode.NotFound));
+        Assert.That(ex.Method, Is.EqualTo("GET"));
+        Assert.That(ex.RequestUri!.Query, Does.Contain("ProfileId="));
+    }
+
     [Test]
     public void CreateAsync_with_invalid_foreign_key_throws_ReCApiException()
     {