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.Infrastructure/Exercises/EfExerciseRepository.cs

@@ -0,0 +1,44 @@
+using Health.Application.Exercises;
+
+namespace Health.Infrastructure.Exercises;
+
+public sealed class EfExerciseRepository(AppDbContext db) : IExerciseRepository
+{
+    private readonly AppDbContext _db = db;
+
+    public async Task<IReadOnlyList<ExercisePlan>> ListActiveOnAsync(Guid userId, DateOnly date, CancellationToken ct) =>
+        await _db.ExercisePlans.Include(p => p.Items)
+            .Where(p => p.UserId == userId && p.StartDate <= date && p.EndDate >= date)
+            .OrderByDescending(p => p.StartDate)
+            .ToListAsync(ct);
+
+    public async Task<IReadOnlyList<ExercisePlan>> ListAsync(Guid userId, int limit, CancellationToken ct) =>
+        await _db.ExercisePlans.Include(p => p.Items)
+            .Where(p => p.UserId == userId)
+            .OrderByDescending(p => p.StartDate)
+            .Take(limit)
+            .ToListAsync(ct);
+
+    public Task<ExercisePlan?> GetOwnedPlanAsync(Guid userId, Guid planId, CancellationToken ct) =>
+        _db.ExercisePlans.Include(p => p.Items)
+            .FirstOrDefaultAsync(p => p.Id == planId && p.UserId == userId, ct);
+
+    public Task<ExercisePlan?> GetLatestAsync(Guid userId, CancellationToken ct) =>
+        _db.ExercisePlans.Include(p => p.Items)
+            .Where(p => p.UserId == userId)
+            .OrderByDescending(p => p.StartDate)
+            .FirstOrDefaultAsync(ct);
+
+    public Task<ExercisePlanItem?> GetOwnedItemAsync(Guid userId, Guid itemId, CancellationToken ct) =>
+        _db.ExercisePlanItems.Include(i => i.Plan)
+            .FirstOrDefaultAsync(i => i.Id == itemId && i.Plan != null && i.Plan.UserId == userId, ct);
+
+    public async Task AddAsync(ExercisePlan plan, CancellationToken ct) =>
+        await _db.ExercisePlans.AddAsync(plan, ct);
+
+    public void Delete(ExercisePlan plan) =>
+        _db.ExercisePlans.Remove(plan);
+
+    public Task SaveChangesAsync(CancellationToken ct) =>
+        _db.SaveChangesAsync(ct);
+}