feat: 应用内通知系统 + 结构化手术史/用药等相关改动

- 新增用户通知 outbox 流水线(EfUserNotificationPipeline)与后台投递 worker
- 通知中心页面及前端通知服务接入
- 健康指标异常、用药/运动提醒等事件统一产出站内通知
- 健康档案结构化手术史、用药提醒扫描、医生/用户端点等配套调整
- AppDbContext 注册通知相关实体

backend/src/Health.Infrastructure/Users/EfUserRepository.cs

@@ -40,6 +40,8 @@ public sealed class EfUserRepository(AppDbContext db) : IUserRepository
         await _db.FollowUps.Where(f => f.UserId == userId).ExecuteDeleteAsync(ct);
         await _db.RefreshTokens.Where(t => t.UserId == userId).ExecuteDeleteAsync(ct);
         await _db.DeviceTokens.Where(t => t.UserId == userId).ExecuteDeleteAsync(ct);
+        await _db.UserNotifications.Where(n => n.UserId == userId).ExecuteDeleteAsync(ct);
+        await _db.NotificationOutbox.Where(n => n.UserId == userId).ExecuteDeleteAsync(ct);
         await _db.NotificationPreferences.Where(p => p.UserId == userId).ExecuteDeleteAsync(ct);
         await _db.HealthArchives.Where(a => a.UserId == userId).ExecuteDeleteAsync(ct);
         await _db.AiWriteCommands.Where(c => c.UserId == userId).ExecuteDeleteAsync(ct);