feat: 新增配额包/支付相关实体与迁移

App：新增 operation_logs/quota_packages/tenant_payments/tenant_quota_package_purchases 表

Identity：修正 Avatar 字段类型（varchar(256)->text），保持现有数据不变

src/Application/TakeoutSaaS.Application/App/Billings/Handlers/UpdateBillStatusCommandHandler.cs

@@ -0,0 +1,50 @@
+using MediatR;
+using TakeoutSaaS.Application.App.Billings.Commands;
+using TakeoutSaaS.Application.App.Billings.Dto;
+using TakeoutSaaS.Domain.Tenants.Repositories;
+using TakeoutSaaS.Shared.Abstractions.Constants;
+using TakeoutSaaS.Shared.Abstractions.Exceptions;
+
+namespace TakeoutSaaS.Application.App.Billings.Handlers;
+
+/// <summary>
+/// 更新账单状态处理器。
+/// </summary>
+public sealed class UpdateBillStatusCommandHandler(
+    ITenantBillingRepository billingRepository,
+    ITenantRepository tenantRepository)
+    : IRequestHandler<UpdateBillStatusCommand, BillDto?>
+{
+    /// <summary>
+    /// 处理更新账单状态请求。
+    /// </summary>
+    /// <param name="request">更新命令。</param>
+    /// <param name="cancellationToken">取消标记。</param>
+    /// <returns>账单 DTO 或 null。</returns>
+    public async Task<BillDto?> Handle(UpdateBillStatusCommand request, CancellationToken cancellationToken)
+    {
+        // 1. 查询账单
+        var bill = await billingRepository.FindByIdAsync(request.BillId, cancellationToken);
+        if (bill is null)
+        {
+            return null;
+        }
+
+        // 2. 更新状态
+        bill.Status = request.Status;
+        if (!string.IsNullOrWhiteSpace(request.Notes))
+        {
+            bill.LineItemsJson = request.Notes;
+        }
+
+        // 3. 持久化变更
+        await billingRepository.UpdateAsync(bill, cancellationToken);
+        await billingRepository.SaveChangesAsync(cancellationToken);
+
+        // 4. 查询租户名称
+        var tenant = await tenantRepository.FindByIdAsync(bill.TenantId, cancellationToken);
+
+        // 5. 返回 DTO
+        return bill.ToDto(tenant?.Name);
+    }
+}