feat: 饮食记录逻辑重构 + 通知管理分隔线修复 + 多页面 UI 调整

- 饮食: 新增 DietCommentaryPolicy + diet_record_logic, 饮食记录逻辑抽取复用
- 通知管理: 分隔线改为仿通知中心样式, 跳过图标区域只留文字下方
- 侧边栏: 对话记录操作栏浮层修复 + 常用功能间距收紧
- 智能体: 欢迎卡片去 400ms 延迟 + 胶囊去阴影
- 后端: AI 会话仓库新增方法 + 饮食评论策略 + 健康记录规则调整
- 其他: api_client IP 适配 + 多页面 UI 微调 + 新增测试

backend/tests/Health.Tests/diet_commentary_tests.cs

@@ -0,0 +1,56 @@
+using Health.Application.AI;
+using Health.Domain.Entities;
+using Health.Domain.Enums;
+
+namespace Health.Tests;
+
+public sealed class DietCommentaryTests
+{
+    [Fact]
+    public void FoodDescription_ContainsOnlyStructuredFoodData()
+    {
+        var result = DietCommentaryPolicy.BuildFoodDescription(
+        [
+            new DietCommentaryFood("番茄炒蛋", "半盘", 220),
+            new DietCommentaryFood("米饭", "一碗", 260),
+        ]);
+
+        Assert.Equal("番茄炒蛋（半盘，220千卡）、米饭（一碗，260千卡）", result);
+        Assert.DoesNotContain("请结合", result);
+    }
+
+    [Fact]
+    public void LegacyArtifact_RequiresEveryUserMessageToUseInternalPrefix()
+    {
+        var artifact = new Conversation
+        {
+            Messages =
+            [
+                new ConversationMessage
+                {
+                    Role = MessageRole.User,
+                    Content = DietCommentaryPolicy.LegacyPromptPrefix + "食物为：米饭",
+                },
+                new ConversationMessage
+                {
+                    Role = MessageRole.Assistant,
+                    Content = "注意搭配蔬菜",
+                },
+            ],
+        };
+        var normal = new Conversation
+        {
+            Messages =
+            [
+                new ConversationMessage
+                {
+                    Role = MessageRole.User,
+                    Content = "我想了解今天的饮食记录",
+                },
+            ],
+        };
+
+        Assert.True(DietCommentaryPolicy.IsLegacyArtifact(artifact.Messages));
+        Assert.False(DietCommentaryPolicy.IsLegacyArtifact(normal.Messages));
+    }
+}