fix: 租户列表接口添加分页支持

- 支持 page 和 pageSize 参数
- 返回 PagedResult<TenantListItemDto>

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

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

@@ -2,6 +2,7 @@ using MediatR;
 using TakeoutSaaS.Application.App.Tenants.Contracts;
 using TakeoutSaaS.Application.App.Tenants.Queries;
 using TakeoutSaaS.Domain.Tenants.Repositories;
+using TakeoutSaaS.Shared.Abstractions.Results;
 
 namespace TakeoutSaaS.Application.App.Tenants.Handlers;
 
@@ -9,16 +10,27 @@ namespace TakeoutSaaS.Application.App.Tenants.Handlers;
 /// 获取租户列表查询处理器。
 /// </summary>
 public sealed class ListTenantsQueryHandler(ITenantRepository tenantRepository)
-    : IRequestHandler<ListTenantsQuery, IReadOnlyList<TenantListItemDto>>
+    : IRequestHandler<ListTenantsQuery, PagedResult<TenantListItemDto>>
 {
     /// <inheritdoc />
-    public async Task<IReadOnlyList<TenantListItemDto>> Handle(ListTenantsQuery request, CancellationToken cancellationToken)
+    public async Task<PagedResult<TenantListItemDto>> Handle(ListTenantsQuery request, CancellationToken cancellationToken)
     {
         // 1. 查询租户列表
         var tenants = await tenantRepository.GetAllAsync(request.Keyword, cancellationToken);
 
-        // 2. 映射 DTO
-        return tenants.Select(t => new TenantListItemDto
+        // 2. 计算分页参数
+        var totalCount = tenants.Count;
+        var page = Math.Max(1, request.Page);
+        var pageSize = Math.Clamp(request.PageSize, 1, 100);
+
+        // 3. 应用分页
+        var pagedTenants = tenants
+            .Skip((page - 1) * pageSize)
+            .Take(pageSize)
+            .ToArray();
+
+        // 4. 映射 DTO
+        var dtos = pagedTenants.Select(t => new TenantListItemDto
         {
             Id = t.Id,
             Code = t.Code,
@@ -26,5 +38,8 @@ public sealed class ListTenantsQueryHandler(ITenantRepository tenantRepository)
             ShortName = t.ShortName,
             Status = t.Status
         }).ToArray();
+
+        // 5. 返回分页结果
+        return new PagedResult<TenantListItemDto>(dtos, page, pageSize, totalCount);
     }
 }

src/Application/TakeoutSaaS.Application/App/Tenants/Queries/ListTenantsQuery.cs

@@ -1,15 +1,26 @@
 using MediatR;
 using TakeoutSaaS.Application.App.Tenants.Contracts;
+using TakeoutSaaS.Shared.Abstractions.Results;
 
 namespace TakeoutSaaS.Application.App.Tenants.Queries;
 
 /// <summary>
 /// 获取租户列表查询（用于下拉选择器）。
 /// </summary>
-public sealed record ListTenantsQuery : IRequest<IReadOnlyList<TenantListItemDto>>
+public sealed record ListTenantsQuery : IRequest<PagedResult<TenantListItemDto>>
 {
     /// <summary>
     /// 关键字（租户名称/编码）。
     /// </summary>
     public string? Keyword { get; init; }
+
+    /// <summary>
+    /// 页码（从 1 开始）。
+    /// </summary>
+    public int Page { get; init; } = 1;
+
+    /// <summary>
+    /// 每页条数。
+    /// </summary>
+    public int PageSize { get; init; } = 20;
 }