feat(admin-api): 实现 TD-001 和 TD-002 后端接口

TD-001 - PUT /api/admin/v1/tenants/{tenantId}:
- 新增 UpdateTenantCommand + UpdateTenantCommandHandler
- Controller 新增 Update 端点（tenant:update 权限）
- 校验：租户存在、name 非空、name/contactPhone 冲突返回 409
- 仓储扩展：ITenantRepository.ExistsByNameAsync

TD-002 - GET /api/admin/v1/tenants/{tenantId}/quota-usage-history:
- 新增 CQRS Query/Handler/DTO/Validator
- 支持分页（Page>=1, PageSize 1~100）
- 支持时间范围和 QuotaType 过滤
- 新增 tenant_quota_usage_histories 表（含迁移）
- 写入点：CheckTenantQuotaCommandHandler + PurchaseQuotaPackageCommandHandler

构建验证：dotnet build 通过
数据库迁移：已应用 20251218121053_AddTenantQuotaUsageHistories

src/Application/TakeoutSaaS.Application/App/QuotaPackages/Handlers/PurchaseQuotaPackageCommandHandler.cs

@@ -2,6 +2,7 @@ using MediatR;
 using TakeoutSaaS.Application.App.QuotaPackages.Commands;
 using TakeoutSaaS.Application.App.QuotaPackages.Dto;
 using TakeoutSaaS.Domain.Tenants.Entities;
+using TakeoutSaaS.Domain.Tenants.Enums;
 using TakeoutSaaS.Domain.Tenants.Repositories;
 using TakeoutSaaS.Shared.Abstractions.Ids;
 
@@ -12,6 +13,7 @@ namespace TakeoutSaaS.Application.App.QuotaPackages.Handlers;
 /// </summary>
 public sealed class PurchaseQuotaPackageCommandHandler(
     IQuotaPackageRepository quotaPackageRepository,
+    ITenantQuotaUsageHistoryRepository quotaUsageHistoryRepository,
     IIdGenerator idGenerator)
     : IRequestHandler<PurchaseQuotaPackageCommand, TenantQuotaPurchaseDto>
 {
@@ -48,8 +50,22 @@ public sealed class PurchaseQuotaPackageCommandHandler(
 
         if (quotaUsage != null)
         {
+            var beforeLimit = quotaUsage.LimitValue;
             quotaUsage.LimitValue += quotaPackage.QuotaValue;
             await quotaPackageRepository.UpdateUsageAsync(quotaUsage, cancellationToken);
+
+            // 4.1 (空行后) 记录配额变更历史（购买配额包视为“剩余增加”）
+            await quotaUsageHistoryRepository.AddAsync(new TenantQuotaUsageHistory
+            {
+                TenantId = request.TenantId,
+                QuotaType = quotaPackage.QuotaType,
+                UsedValue = quotaUsage.UsedValue,
+                LimitValue = quotaUsage.LimitValue,
+                RecordedAt = DateTime.UtcNow,
+                ChangeType = TenantQuotaUsageHistoryChangeType.Increase,
+                ChangeAmount = quotaUsage.LimitValue - beforeLimit,
+                ChangeReason = $"购买配额包：{quotaPackage.Name}"
+            }, cancellationToken);
         }
 
         await quotaPackageRepository.SaveChangesAsync(cancellationToken);