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

health_app/test/diet_meal_selection_test.dart

@@ -0,0 +1,12 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:health_app/pages/diet/diet_capture_page.dart';
+
+void main() {
+  test('new diet analysis requires the user to choose a meal type', () {
+    final container = ProviderContainer();
+    addTearDown(container.dispose);
+
+    expect(container.read(dietProvider).mealType, isEmpty);
+  });
+}

health_app/test/diet_record_logic_test.dart

@@ -0,0 +1,18 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:health_app/pages/diet/diet_record_logic.dart';
+
+void main() {
+  test('recent diet dates end with today', () {
+    final now = DateTime(2026, 7, 12, 21, 30);
+
+    final dates = recentDietDates(now);
+
+    expect(dates, hasLength(7));
+    expect(dates.first, DateTime(2026, 7, 6));
+    expect(dates.last, DateTime(2026, 7, 12));
+  });
+
+  test('blank food draft is not valid for saving', () {
+    expect(isSavableFood(name: '', portion: '', calories: 0), isFalse);
+  });
+}