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/Infrastructure/TakeoutSaaS.Infrastructure/BackgroundServices/SubscriptionExpiryCheckService.cs

@@ -0,0 +1,132 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using TakeoutSaaS.Domain.Tenants.Enums;
+using TakeoutSaaS.Infrastructure.App.Persistence;
+
+namespace TakeoutSaaS.Infrastructure.BackgroundServices;
+
+/// <summary>
+/// 订阅到期检查后台服务。
+/// 每天凌晨执行，检查即将到期和已到期的订阅，自动更新状态。
+/// </summary>
+public sealed class SubscriptionExpiryCheckService : BackgroundService
+{
+    private readonly IServiceProvider _serviceProvider;
+    private readonly ILogger<SubscriptionExpiryCheckService> _logger;
+    private readonly SubscriptionExpiryCheckOptions _options;
+
+    public SubscriptionExpiryCheckService(
+        IServiceProvider serviceProvider,
+        ILogger<SubscriptionExpiryCheckService> logger,
+        IOptions<SubscriptionExpiryCheckOptions> options)
+    {
+        _serviceProvider = serviceProvider;
+        _logger = logger;
+        _options = options.Value;
+    }
+
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        _logger.LogInformation("订阅到期检查服务已启动");
+
+        while (!stoppingToken.IsCancellationRequested)
+        {
+            try
+            {
+                // 计算下次执行时间（每天凌晨）
+                var now = DateTime.UtcNow;
+                var nextRun = now.Date.AddDays(1).AddHours(_options.ExecuteHour);
+                var delay = nextRun - now;
+
+                _logger.LogInformation("订阅到期检查服务将在 {NextRun} 执行，等待 {Delay}", nextRun, delay);
+
+                await Task.Delay(delay, stoppingToken);
+
+                if (stoppingToken.IsCancellationRequested)
+                    break;
+
+                await CheckExpiringSubscriptionsAsync(stoppingToken);
+            }
+            catch (Exception ex)
+            {
+                _logger.LogError(ex, "订阅到期检查服务执行异常");
+                // 出错后等待一段时间再重试
+                await Task.Delay(TimeSpan.FromMinutes(5), stoppingToken);
+            }
+        }
+
+        _logger.LogInformation("订阅到期检查服务已停止");
+    }
+
+    private async Task CheckExpiringSubscriptionsAsync(CancellationToken cancellationToken)
+    {
+        _logger.LogInformation("开始执行订阅到期检查");
+
+        using var scope = _serviceProvider.CreateScope();
+        var dbContext = scope.ServiceProvider.GetRequiredService<TakeoutAppDbContext>();
+
+        var now = DateTime.UtcNow;
+        var gracePeriodDays = _options.GracePeriodDays;
+
+        try
+        {
+            // 1. 检查活跃订阅中已到期的，转为宽限期
+            var expiredActive = await dbContext.TenantSubscriptions
+                .Where(s => s.Status == SubscriptionStatus.Active && s.EffectiveTo < now)
+                .ToListAsync(cancellationToken);
+
+            foreach (var subscription in expiredActive)
+            {
+                subscription.Status = SubscriptionStatus.GracePeriod;
+                _logger.LogInformation(
+                    "订阅 {SubscriptionId} (租户 {TenantId}) 已到期，进入宽限期",
+                    subscription.Id, subscription.TenantId);
+            }
+
+            // 2. 检查宽限期订阅中超过宽限期的，转为暂停
+            var gracePeriodExpired = await dbContext.TenantSubscriptions
+                .Where(s => s.Status == SubscriptionStatus.GracePeriod
+                         && s.EffectiveTo.AddDays(gracePeriodDays) < now)
+                .ToListAsync(cancellationToken);
+
+            foreach (var subscription in gracePeriodExpired)
+            {
+                subscription.Status = SubscriptionStatus.Suspended;
+                _logger.LogInformation(
+                    "订阅 {SubscriptionId} (租户 {TenantId}) 宽限期已结束，已暂停",
+                    subscription.Id, subscription.TenantId);
+            }
+
+            // 3. 保存更改
+            var changedCount = await dbContext.SaveChangesAsync(cancellationToken);
+
+            _logger.LogInformation(
+                "订阅到期检查完成，共更新 {Count} 条记录 (到期转宽限期: {ExpiredCount}, 宽限期转暂停: {SuspendedCount})",
+                changedCount, expiredActive.Count, gracePeriodExpired.Count);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "订阅到期检查失败");
+            throw;
+        }
+    }
+}
+
+/// <summary>
+/// 订阅到期检查配置选项。
+/// </summary>
+public sealed class SubscriptionExpiryCheckOptions
+{
+    /// <summary>
+    /// 执行时间（小时，UTC时间），默认凌晨2点。
+    /// </summary>
+    public int ExecuteHour { get; set; } = 2;
+
+    /// <summary>
+    /// 宽限期天数，默认7天。
+    /// </summary>
+    public int GracePeriodDays { get; set; } = 7;
+}