feat(tutorial): add /tutorial/update — echo step + persist to viewer

POST /tutorial/update echoes tutorial_step back and saves it to
Viewer.MissionData.TutorialState. is_skip=1 is handled server-side
by honoring whatever tutorial_step value the client sends (client
already sends 100 when skipping). Adds TutorialUpdateRequest DTO,
TutorialUpdateResponse DTO, injects SVSimDbContext into
TutorialController, and adds GetViewerTutorialStateAsync helper to
SVSimTestFactory.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SVSim.EmulatedEntrypoint/Models/Dtos/Requests/Tutorial/TutorialUpdateRequest.cs

@@ -0,0 +1,23 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Requests;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Requests.Tutorial;
+
+/// <summary>
+/// <c>POST /tutorial/update</c> — client reports the step it is moving TO.
+/// Client task: <c>Wizard/TutorialUpdateTask.cs</c>.
+/// </summary>
+[MessagePackObject]
+public class TutorialUpdateRequest : BaseRequest
+{
+    /// <summary>The tutorial step the client is moving TO (0, 1, 11, 21, 31, 41, 100).</summary>
+    [JsonPropertyName("tutorial_step")]
+    [Key("tutorial_step")]
+    public int TutorialStep { get; set; }
+
+    /// <summary>0 = normal, 1 = user chose Skip Tutorial.</summary>
+    [JsonPropertyName("is_skip")]
+    [Key("is_skip")]
+    public int IsSkip { get; set; }
+}