feat: 管理端核心实体CRUD补齐

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

@@ -0,0 +1,40 @@
+using MediatR;
+using Microsoft.Extensions.Logging;
+using TakeoutSaaS.Application.App.Merchants.Commands;
+using TakeoutSaaS.Domain.Merchants.Repositories;
+using TakeoutSaaS.Shared.Abstractions.Tenancy;
+
+namespace TakeoutSaaS.Application.App.Merchants.Handlers;
+
+/// <summary>
+/// 删除商户命令处理器。
+/// </summary>
+public sealed class DeleteMerchantCommandHandler(
+    IMerchantRepository merchantRepository,
+    ITenantProvider tenantProvider,
+    ILogger<DeleteMerchantCommandHandler> logger)
+    : IRequestHandler<DeleteMerchantCommand, bool>
+{
+    private readonly IMerchantRepository _merchantRepository = merchantRepository;
+    private readonly ITenantProvider _tenantProvider = tenantProvider;
+    private readonly ILogger<DeleteMerchantCommandHandler> _logger = logger;
+
+    /// <inheritdoc />
+    public async Task<bool> Handle(DeleteMerchantCommand request, CancellationToken cancellationToken)
+    {
+        // 1. 校验存在性
+        var tenantId = _tenantProvider.GetCurrentTenantId();
+        var existing = await _merchantRepository.FindByIdAsync(request.MerchantId, tenantId, cancellationToken);
+        if (existing == null)
+        {
+            return false;
+        }
+
+        // 2. 删除
+        await _merchantRepository.DeleteMerchantAsync(request.MerchantId, tenantId, cancellationToken);
+        await _merchantRepository.SaveChangesAsync(cancellationToken);
+        _logger.LogInformation("删除商户 {MerchantId}", request.MerchantId);
+
+        return true;
+    }
+}