feat(tutorial): add /tutorial/gift_top with hardcoded starter present list

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

SVSim.Database/Migrations/20260528160031_AddViewerClaimedTutorialGift.cs

@@ -0,0 +1,41 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace SVSim.Database.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddViewerClaimedTutorialGift : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "ViewerClaimedTutorialGifts",
+                columns: table => new
+                {
+                    ViewerId = table.Column<long>(type: "bigint", nullable: false),
+                    PresentId = table.Column<string>(type: "character varying(64)", maxLength: 64, nullable: false),
+                    ClaimedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_ViewerClaimedTutorialGifts", x => new { x.ViewerId, x.PresentId });
+                    table.ForeignKey(
+                        name: "FK_ViewerClaimedTutorialGifts_Viewers_ViewerId",
+                        column: x => x.ViewerId,
+                        principalTable: "Viewers",
+                        principalColumn: "Id",
+                        onDelete: ReferentialAction.Cascade);
+                });
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "ViewerClaimedTutorialGifts");
+        }
+    }
+}