chore: add documentation comments and stylecop rules

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

@@ -14,19 +14,23 @@ public sealed class MarkTenantBillingPaidCommandHandler(ITenantBillingRepository
 {
     public async Task<TenantBillingDto?> Handle(MarkTenantBillingPaidCommand request, CancellationToken cancellationToken)
     {
+        // 1. 查询账单
         var bill = await billingRepository.FindByIdAsync(request.TenantId, request.BillingId, cancellationToken);
         if (bill == null)
         {
             return null;
         }
 
+        // 2. 更新支付状态
         bill.AmountPaid = request.AmountPaid;
         bill.Status = TenantBillingStatus.Paid;
         bill.DueDate = bill.DueDate;
 
+        // 3. 持久化变更
         await billingRepository.UpdateAsync(bill, cancellationToken);
         await billingRepository.SaveChangesAsync(cancellationToken);
 
+        // 4. 返回 DTO
         return bill.ToDto();
     }
 }