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/AI/AiConversationContracts.cs

@@ -0,0 +1,63 @@
+using Health.Domain.Entities;
+using Health.Domain.Enums;
+
+namespace Health.Application.AI;
+
+public sealed record AiConversationDto(
+    Guid Id,
+    string AgentType,
+    string? Title,
+    string? Summary,
+    int MessageCount,
+    DateTime CreatedAt,
+    DateTime UpdatedAt);
+
+public sealed record AiConversationMessageDto(
+    Guid Id,
+    string Role,
+    string Content,
+    string? Intent,
+    string? MetadataJson,
+    DateTime CreatedAt);
+
+public sealed record OpenConversationResult(
+    bool Found,
+    bool Created,
+    Guid ConversationId);
+
+public interface IAiConversationService
+{
+    Task<OpenConversationResult> OpenAsync(Guid userId, Guid? conversationId, AgentType agentType, string firstMessage, CancellationToken ct);
+    Task AddUserMessageAsync(Guid conversationId, string content, CancellationToken ct);
+    Task AddAssistantMessageAsync(Guid conversationId, string content, CancellationToken ct);
+    Task<IReadOnlyList<AiConversationMessageDto>> GetRecentMessagesAsync(Guid conversationId, int limit, CancellationToken ct);
+    Task<IReadOnlyList<AiConversationDto>> ListAsync(Guid userId, CancellationToken ct);
+    Task<IReadOnlyList<AiConversationMessageDto>> GetMessagesAsync(Guid userId, Guid conversationId, CancellationToken ct);
+    Task DeleteAsync(Guid userId, Guid conversationId, CancellationToken ct);
+}
+
+public interface IAiConversationRepository
+{
+    Task<Conversation?> GetOwnedAsync(Guid userId, Guid conversationId, CancellationToken ct);
+    Task<Conversation?> GetAsync(Guid conversationId, CancellationToken ct);
+    Task<IReadOnlyList<Conversation>> ListAsync(Guid userId, CancellationToken ct);
+    Task<IReadOnlyList<ConversationMessage>> GetMessagesAsync(Guid conversationId, CancellationToken ct);
+    Task<IReadOnlyList<ConversationMessage>> GetRecentMessagesAsync(Guid conversationId, int limit, CancellationToken ct);
+    Task AddConversationAsync(Conversation conversation, CancellationToken ct);
+    Task AddMessageAsync(ConversationMessage message, CancellationToken ct);
+    void Delete(Conversation conversation);
+    Task SaveChangesAsync(CancellationToken ct);
+}
+
+public interface IPatientContextService
+{
+    Task<string> BuildAsync(Guid userId, CancellationToken ct);
+}
+
+public sealed record AiConfirmedWriteResult(int Code, object? Data, string? Message);
+
+public interface IAiToolExecutionService
+{
+    Task<object> ExecuteAsync(string toolName, string arguments, Guid userId, CancellationToken ct);
+    Task<AiConfirmedWriteResult> ConfirmAsync(Guid commandId, Guid userId, CancellationToken ct);
+}