feat: 商户模块移除租户上下文依赖

src/Application/TakeoutSaaS.Application/App/Merchants/Handlers/CreateMerchantCommandHandler.cs

@@ -20,6 +20,7 @@ public sealed class CreateMerchantCommandHandler(IMerchantRepository merchantRep
         // 1. 构建商户实体
         var merchant = new Merchant
         {
+            TenantId = request.TenantId,
             BrandName = request.BrandName.Trim(),
             BrandAlias = request.BrandAlias?.Trim(),
             LogoUrl = request.LogoUrl?.Trim(),