feat(campaign): CampaignController.RegisterSerialCode + DTOs + tests

Adds POST /campaign/regist_serial_code with 9 integration tests covering
success path, all disqualifier conditions (unknown/disabled/expired/future/
already-redeemed/unsupported-reward-type), 401 on missing auth, and case-
sensitivity. IsSupportedGiftRewardType uses gift-wire literals (1/4/9) not
UserGoodsType enum values, matching GiftController.WireRewardTypeToUserGoodsType.

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

SVSim.EmulatedEntrypoint/Controllers/CampaignController.cs

@@ -0,0 +1,93 @@
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+using SVSim.Database;
+using SVSim.Database.Enums;
+using SVSim.Database.Models;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Campaign;
+
+namespace SVSim.EmulatedEntrypoint.Controllers;
+
+/// <summary>
+/// /campaign/* — promotional surfaces. Currently just <c>regist_serial_code</c>.
+/// </summary>
+[Route("campaign")]
+public sealed class CampaignController : SVSimController
+{
+    private const int FailureResultCode = 4202;
+
+    private readonly SVSimDbContext _db;
+
+    public CampaignController(SVSimDbContext db) => _db = db;
+
+    [HttpPost("regist_serial_code")]
+    public async Task<IActionResult> RegisterSerialCode(
+        [FromBody] RegisterSerialCodeRequest request,
+        CancellationToken ct)
+    {
+        if (!TryGetViewerId(out var viewerId)) return Unauthorized();
+
+        var now = DateTime.UtcNow;
+
+        var code = await _db.SerialCodes
+            .Include(c => c.Rewards)
+            .FirstOrDefaultAsync(c => c.Code == request.SerialCode, ct);
+
+        if (code is null) return Fail();
+        if (!code.IsEnabled) return Fail();
+        if (code.StartAt is { } start && start > now) return Fail();
+        if (code.EndAt is { } end && end < now) return Fail();
+
+        bool alreadyRedeemed = await _db.ViewerSerialCodeRedemptions
+            .AnyAsync(r => r.ViewerId == viewerId && r.SerialCodeId == code.Id, ct);
+        if (alreadyRedeemed) return Fail();
+
+        if (code.Rewards.Any(r => !IsSupportedGiftRewardType(r.RewardType))) return Fail();
+
+        try
+        {
+            _db.ViewerSerialCodeRedemptions.Add(new ViewerSerialCodeRedemption
+            {
+                ViewerId = viewerId,
+                SerialCodeId = code.Id,
+                RedeemedAt = now,
+            });
+
+            foreach (var reward in code.Rewards.OrderBy(r => r.Slot))
+            {
+                _db.ViewerPresents.Add(new ViewerPresent
+                {
+                    ViewerId = viewerId,
+                    PresentId = Guid.NewGuid().ToString("N").Substring(0, 16),
+                    Status = PresentStatus.Unclaimed,
+                    RewardType = reward.RewardType,
+                    RewardDetailId = reward.RewardDetailId,
+                    RewardCount = reward.RewardCount,
+                    Message = code.Message,
+                    CreatedAt = now,
+                    Source = $"serial_code:{code.Id}",
+                });
+            }
+
+            await _db.SaveChangesAsync(ct);
+        }
+        catch (DbUpdateException)
+        {
+            // Race: two concurrent redeems for the same (viewer, code). The composite PK
+            // on ViewerSerialCodeRedemption rejects the second one; treat as already-redeemed.
+            return Fail();
+        }
+
+        return Ok(new RegisterSerialCodeResponse { IsComplete = true });
+    }
+
+    private IActionResult Fail() => Ok(new { result_code = FailureResultCode });
+
+    /// <summary>
+    /// Gift wire types per <c>GiftController.WireRewardTypeToUserGoodsType</c>:
+    /// 1=Crystal, 4=Item, 9=Rupy. Codes with unsupported types fail-fast at redemption.
+    /// Note: wire "1" means Crystal (not RedEther), following the gift wire convention
+    /// rather than the <see cref="UserGoodsType"/> enum order.
+    /// </summary>
+    private static bool IsSupportedGiftRewardType(int rewardType) =>
+        rewardType is 1 or 4 or 9;
+}

SVSim.EmulatedEntrypoint/Models/Dtos/Campaign/RegisterSerialCodeRequest.cs

@@ -0,0 +1,17 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Campaign;
+
+/// <summary>
+/// Body of <c>POST /campaign/regist_serial_code</c>. Client task:
+/// <c>MyPageCodeInputTask</c> (Shadowverse_Code_2026-05-23/Wizard/MyPageCodeInputTask.cs).
+/// </summary>
+[MessagePackObject]
+public sealed class RegisterSerialCodeRequest
+{
+    /// <summary>User-typed serial code. Case-sensitive on the server.</summary>
+    [JsonPropertyName("serial_code")]
+    [Key("serial_code")]
+    public string SerialCode { get; set; } = string.Empty;
+}

SVSim.EmulatedEntrypoint/Models/Dtos/Campaign/RegisterSerialCodeResponse.cs

@@ -0,0 +1,16 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Campaign;
+
+/// <summary>
+/// Success response shape. Failure path uses an anonymous <c>{ result_code = 4202 }</c>
+/// (mirroring AchievementController/MissionController) and bypasses this DTO.
+/// </summary>
+[MessagePackObject]
+public sealed class RegisterSerialCodeResponse
+{
+    [JsonPropertyName("is_complete")]
+    [Key("is_complete")]
+    public bool IsComplete { get; set; }
+}