refactor(tutorial-presents): promote static catalogue to seed-driven TutorialPresentEntries table

The five tutorial gifts every fresh viewer is given at signup used to live as a
static C# array in SVSim.Database/SeedData/TutorialPresents.cs — outside the
seed-JSON pipeline used by all 40+ other globals tables. Editing a gift required
a code change + rebuild instead of a JSON edit + bootstrap re-run.

Now authored in SVSim.Bootstrap/Data/seeds/tutorial-presents.json and loaded into
a new TutorialPresentEntries table via TutorialPresentsImporter (clear-and-rewrite,
mirroring HomeDialogs). ViewerRepository.RegisterAnonymousViewer reads the table
at signup and projects each row into a ViewerPresent with Source="tutorial".

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.Database/Migrations/20260609132350_AddTutorialPresentEntries.cs

@@ -0,0 +1,37 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace SVSim.Database.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddTutorialPresentEntries : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "TutorialPresentEntries",
+                columns: table => new
+                {
+                    PresentId = table.Column<string>(type: "character varying(64)", maxLength: 64, nullable: false),
+                    RewardType = table.Column<int>(type: "integer", nullable: false),
+                    RewardDetailId = table.Column<long>(type: "bigint", nullable: false),
+                    RewardCount = table.Column<long>(type: "bigint", nullable: false),
+                    ItemType = table.Column<int>(type: "integer", nullable: true),
+                    Message = table.Column<string>(type: "text", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_TutorialPresentEntries", x => x.PresentId);
+                });
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "TutorialPresentEntries");
+        }
+    }
+}