chore: add documentation comments and stylecop rules

src/Application/TakeoutSaaS.Application/App/Tenants/Handlers/CreateTenantBillingCommandHandler.cs

@@ -16,11 +16,13 @@ public sealed class CreateTenantBillingCommandHandler(ITenantBillingRepository b
 {
     public async Task<TenantBillingDto> Handle(CreateTenantBillingCommand request, CancellationToken cancellationToken)
     {
+        // 1. 校验账单编号
         if (string.IsNullOrWhiteSpace(request.StatementNo))
         {
             throw new BusinessException(ErrorCodes.BadRequest, "账单编号不能为空");
         }
 
+        // 2. 构建账单实体
         var bill = new TenantBillingStatement
         {
             TenantId = request.TenantId,
@@ -34,9 +36,11 @@ public sealed class CreateTenantBillingCommandHandler(ITenantBillingRepository b
             LineItemsJson = request.LineItemsJson
         };
 
+        // 3. 持久化账单
         await billingRepository.AddAsync(bill, cancellationToken);
         await billingRepository.SaveChangesAsync(cancellationToken);
 
+        // 4. 返回 DTO
         return bill.ToDto();
     }
 }