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/Diets/DietImageAnalyzer.cs

@@ -0,0 +1,42 @@
+using Health.Application.Diets;
+using Health.Infrastructure.AI;
+
+namespace Health.Infrastructure.Diets;
+
+public sealed class DietImageAnalyzer(VisionClient vision) : IDietImageAnalyzer
+{
+    private readonly VisionClient _vision = vision;
+
+    public async Task<DietImageAnalysisResult> AnalyzeAsync(DietImageAnalysisJob job, CancellationToken ct)
+    {
+        var imageUrls = new List<string>();
+        foreach (var filePath in job.FilePaths)
+        {
+            if (!File.Exists(filePath))
+                return new DietImageAnalysisResult(false, 40004, null, "待识别图片不存在");
+
+            var bytes = await File.ReadAllBytesAsync(filePath, ct);
+            var base64 = Convert.ToBase64String(bytes);
+            if (base64.Length > 7 * 1024 * 1024)
+                return new DietImageAnalysisResult(false, 40001, null, "图片过大，请压缩后重新上传");
+
+            var extension = Path.GetExtension(filePath).ToLowerInvariant();
+            var mime = extension switch
+            {
+                ".png" => "image/png",
+                ".heic" => "image/heic",
+                _ => "image/jpeg"
+            };
+            imageUrls.Add($"data:{mime};base64,{base64}");
+        }
+
+        var prompt = """
+            识别图片中的食物和饮品，返回JSON数组：
+            [{"name":"名称","portion":"份量","calories":热量}]
+            只返回JSON，不要其他内容。
+            """;
+        var response = await _vision.VisionAsync(prompt, imageUrls, userText: null, maxTokens: 8192, ct: ct);
+        var result = response.Choices?.FirstOrDefault()?.Message?.Content ?? "[]";
+        return new DietImageAnalysisResult(true, 0, result, null);
+    }
+}