feat: 后端架构重构 — Endpoint→Service→Repository分层 + AI确认机制 + 异步任务持久化

- 核心业务拆分为 Endpoint → Application Service → Repository 三层
- AI写入操作必须用户确认后才写库(确认卡片机制)
- 报告/饮食/用药分析改为持久化任务队列(原子领取/重试/重启恢复)
- 运动计划修复: 连续真实日期替代周模板
- 用药提醒去重 + 通知Outbox预留
- 认证收拢到AuthService, 管理员收拢到AdminService
- AI会话加用户归属校验防串号
- 提示词调整为患者视角
- 开发假数据已关闭
- 21/21测试通过, 0警告0错误

backend/src/Health.Application/Calendars/CalendarContracts.cs

@@ -0,0 +1,19 @@
+using Health.Domain.Entities;
+
+namespace Health.Application.Calendars;
+
+public sealed record CalendarDataSnapshot(
+    IReadOnlyList<Medication> Medications,
+    IReadOnlyList<ExercisePlan> ExercisePlans,
+    IReadOnlyList<FollowUp> FollowUps);
+
+public interface ICalendarService
+{
+    Task<IReadOnlyList<object>> GetMonthAsync(Guid userId, int year, int month, CancellationToken ct);
+    Task<object> GetDayAsync(Guid userId, DateOnly date, CancellationToken ct);
+}
+
+public interface ICalendarRepository
+{
+    Task<CalendarDataSnapshot> GetSnapshotAsync(Guid userId, DateOnly start, DateOnly end, CancellationToken ct);
+}