feat: UI 系统中心化 + 趋势图重构 + 法律文档 H5 上线

- UI 系统: 新增 design_tokens / module_visuals / app_buttons / app_status_badge / app_toast / ai_content 六个共享模块; 28 个页面接入, SnackBar 全部替换为 AppToast
- 趋势图: 直线折线 + 渐变填充 + 阴影; 去网格线; X 轴日+月份分隔; Y 轴整数刻度最多 4 个; 点击数据点/录入记录显示上方浮层, 选中点变实心
- 法律文档 H5: 后端 wwwroot 托管隐私政策/服务协议/关于/个人信息收集清单/第三方 SDK 清单 + 索引页; Program.cs 启用 UseDefaultFiles + UseStaticFiles
- 其他: auth_provider 登录流程调整; api_client IP 适配; 主页智能体栏间距优化

health_app/lib/widgets/ai_content.dart

@@ -0,0 +1,87 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_markdown/flutter_markdown.dart';
+
+import '../core/app_colors.dart';
+import '../core/app_design_tokens.dart';
+
+class AiContent {
+  AiContent._();
+
+  static String clean(String text) {
+    var t = text;
+    t = t.replaceAll(RegExp(r'\$\d+'), '');
+    t = t.replaceAll(RegExp(r'<[^>]+>'), '');
+    t = t.replaceAllMapped(RegExp(r'^#{4,}\s', multiLine: true), (_) => '### ');
+    t = t.replaceAll(RegExp(r'\n{3,}'), '\n\n');
+    return t.trim();
+  }
+
+  static String plain(String text) {
+    final cleaned = clean(text);
+    return cleaned
+        .replaceAll(RegExp(r'\*\*(.*?)\*\*'), r'$1')
+        .replaceAll(RegExp(r'__(.*?)__'), r'$1')
+        .replaceAll(RegExp(r'`([^`]+)`'), r'$1')
+        .replaceAll(RegExp(r'^\s*[-*]\s+', multiLine: true), '• ')
+        .trim();
+  }
+}
+
+class AiMarkdownView extends StatelessWidget {
+  final String data;
+  final bool selectable;
+  final void Function(String text, String? href, String title)? onTapLink;
+
+  const AiMarkdownView({
+    super.key,
+    required this.data,
+    this.selectable = true,
+    this.onTapLink,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return MarkdownBody(
+      data: AiContent.clean(data),
+      selectable: selectable,
+      onTapLink: onTapLink,
+      styleSheet: MarkdownStyleSheet(
+        p: AppTextStyles.chatBody,
+        a: AppTextStyles.chatBody.copyWith(
+          color: AppColors.primary,
+          fontWeight: FontWeight.w800,
+          decoration: TextDecoration.underline,
+          decorationColor: AppColors.primary,
+        ),
+        strong: AppTextStyles.chatBody.copyWith(fontWeight: FontWeight.w800),
+        h1: AppTextStyles.chatTitle.copyWith(fontSize: 20),
+        h2: AppTextStyles.chatTitle.copyWith(fontSize: 20),
+        h3: AppTextStyles.chatTitle.copyWith(fontSize: 19),
+        listBullet: AppTextStyles.chatBody.copyWith(
+          fontSize: 21,
+          fontWeight: FontWeight.w900,
+        ),
+        listBulletPadding: const EdgeInsets.only(right: 8),
+        blockquote: AppTextStyles.chatBody.copyWith(color: AppColors.textSecondary),
+      ),
+    );
+  }
+}
+
+class AiGeneratedNote extends StatelessWidget {
+  const AiGeneratedNote({super.key});
+
+  @override
+  Widget build(BuildContext context) => const Padding(
+    padding: EdgeInsets.only(top: 10),
+    child: Row(
+      mainAxisSize: MainAxisSize.min,
+      children: [
+        Icon(Icons.auto_awesome_rounded, size: 15, color: AppColors.textHint),
+        SizedBox(width: 5),
+        Text('内容由 AI 生成', style: AppTextStyles.aiNote),
+      ],
+    ),
+  );
+}
+