✨ feat: 完成账单管理模块后端功能开发及API优化

核心功能:
- 账单CRUD操作（创建、查询、详情、更新状态、删除）
- 支付记录管理（创建支付、审核支付）
- 批量操作支持（批量更新账单状态）
- 统计分析功能（账单统计、逾期账单查询）
- 导出功能（Excel/PDF/CSV）

API端点 (16个):
- GET /api/admin/v1/billings - 账单列表（分页、筛选、排序）
- POST /api/admin/v1/billings - 创建账单
- GET /api/admin/v1/billings/{id} - 账单详情
- DELETE /api/admin/v1/billings/{id} - 删除账单
- PUT /api/admin/v1/billings/{id}/status - 更新状态
- POST /api/admin/v1/billings/batch/status - 批量更新
- GET /api/admin/v1/billings/{id}/payments - 支付记录
- POST /api/admin/v1/billings/{id}/payments - 创建支付
- PUT /api/admin/v1/billings/payments/{paymentId}/verify - 审核支付
- GET /api/admin/v1/billings/statistics - 统计数据
- GET /api/admin/v1/billings/overdue - 逾期账单
- POST /api/admin/v1/billings/export - 导出账单

架构优化:
- 采用CQRS模式分离读写（MediatR + Dapper + EF Core）
- 完整的领域模型设计（TenantBillingStatement, TenantPayment等）
- FluentValidation请求验证
- 状态机管理账单和支付状态流转

API设计优化 (三项改进):
1. 导出API响应Content-Type改为application/octet-stream
2. 支付审核API添加Approved和Notes可选参数，支持通过/拒绝
3. 移除TenantBillings API中重复的TenantId参数

数据库变更:
- 新增账单相关表及关系
- 支持Snowflake ID主键
- 完整的审计字段支持

🤖 Generated with Claude Code

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

src/Infrastructure/TakeoutSaaS.Infrastructure/App/Extensions/AppServiceCollectionExtensions.cs

@@ -8,9 +8,12 @@ using TakeoutSaaS.Domain.Payments.Repositories;
 using TakeoutSaaS.Domain.Products.Repositories;
 using TakeoutSaaS.Domain.Stores.Repositories;
 using TakeoutSaaS.Domain.Tenants.Repositories;
+using TakeoutSaaS.Domain.Tenants.Services;
 using TakeoutSaaS.Infrastructure.App.Options;
 using TakeoutSaaS.Infrastructure.App.Persistence;
+using TakeoutSaaS.Infrastructure.App.Persistence.Repositories;
 using TakeoutSaaS.Infrastructure.App.Repositories;
+using TakeoutSaaS.Infrastructure.App.Services;
 using TakeoutSaaS.Infrastructure.Common.Extensions;
 using TakeoutSaaS.Shared.Abstractions.Constants;
 
@@ -40,8 +43,8 @@ public static class AppServiceCollectionExtensions
         services.AddScoped<IPaymentRepository, EfPaymentRepository>();
         services.AddScoped<IDeliveryRepository, EfDeliveryRepository>();
         services.AddScoped<ITenantRepository, EfTenantRepository>();
-        services.AddScoped<ITenantBillingRepository, EfTenantBillingRepository>();
-        services.AddScoped<ITenantPaymentRepository, EfTenantPaymentRepository>();
+        services.AddScoped<ITenantBillingRepository, TenantBillingRepository>();
+        services.AddScoped<ITenantPaymentRepository, TenantPaymentRepository>();
         services.AddScoped<ITenantAnnouncementRepository, EfTenantAnnouncementRepository>();
         services.AddScoped<ITenantAnnouncementReadRepository, EfTenantAnnouncementReadRepository>();
         services.AddScoped<ITenantNotificationRepository, EfTenantNotificationRepository>();
@@ -52,6 +55,10 @@ public static class AppServiceCollectionExtensions
         services.AddScoped<IStatisticsRepository, EfStatisticsRepository>();
         services.AddScoped<ISubscriptionRepository, EfSubscriptionRepository>();
 
+        // 1. 账单领域/导出服务
+        services.AddScoped<IBillingDomainService, BillingDomainService>();
+        services.AddScoped<IBillingExportService, BillingExportService>();
+
         services.AddOptions<AppSeedOptions>()
             .Bind(configuration.GetSection(AppSeedOptions.SectionName))
             .ValidateDataAnnotations();