新增定时账单功能

Service/PeriodicBillBackgroundService.cs

@@ -0,0 +1,61 @@
+using Microsoft.Extensions.Hosting;
+
+namespace Service;
+
+/// <summary>
+/// 周期性账单后台服务
+/// </summary>
+public class PeriodicBillBackgroundService(
+    IServiceProvider serviceProvider,
+    ILogger<PeriodicBillBackgroundService> logger
+) : BackgroundService
+{
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        logger.LogInformation("周期性账单后台服务已启动");
+
+        while (!stoppingToken.IsCancellationRequested)
+        {
+            try
+            {
+                var now = DateTime.Now;
+                
+                // 计算下次执行时间（每天早上6点）
+                var nextRun = now.Date.AddHours(6);
+                if (now >= nextRun)
+                {
+                    nextRun = nextRun.AddDays(1);
+                }
+
+                var delay = nextRun - now;
+                logger.LogInformation("下次执行周期性账单检查时间: {NextRun}, 延迟: {Delay}", 
+                    nextRun.ToString("yyyy-MM-dd HH:mm:ss"), delay);
+
+                await Task.Delay(delay, stoppingToken);
+
+                if (stoppingToken.IsCancellationRequested)
+                    break;
+
+                // 执行周期性账单检查
+                using (var scope = serviceProvider.CreateScope())
+                {
+                    var periodicService = scope.ServiceProvider.GetRequiredService<ITransactionPeriodicService>();
+                    await periodicService.ExecutePeriodicBillsAsync();
+                }
+            }
+            catch (OperationCanceledException)
+            {
+                logger.LogInformation("周期性账单后台服务已取消");
+                break;
+            }
+            catch (Exception ex)
+            {
+                logger.LogError(ex, "周期性账单后台服务执行出错");
+                // 出错后等待1小时再重试
+                await Task.Delay(TimeSpan.FromHours(1), stoppingToken);
+            }
+        }
+
+        logger.LogInformation("周期性账单后台服务已停止");
+    }
+}