feat: UI 清新风全面改造 — 朝露主题 + shadcn_ui + 全局字号放大

- 全新"朝露"主题：深青绿主色(#2D6A4F)，暖白底，完整设计Token
- 引入 shadcn_ui 组件库，MaterialApp 注入 ShadTheme
- 新增 4 个公共组件：AppCard、AppMenuItem、AppEmptyState、AppTabChip
- 全面消除硬编码颜色，统一使用 AppTheme Token
- 全局字号 +3~4pt，图标等比放大 +3px
- home/medication/profile/settings/login 等核心页面重写
- 路由和功能逻辑零改动

health_app/lib/widgets/app_menu_item.dart

@@ -0,0 +1,67 @@
+import 'package:flutter/material.dart';
+import 'package:shadcn_ui/shadcn_ui.dart';
+import '../core/app_theme.dart';
+
+/// 统一菜单项，profile_page 和 settings_pages 都共用这个
+class AppMenuItem extends StatelessWidget {
+  final IconData icon;
+  final String title;
+  final String? subtitle;
+  final String? trailing;
+  final VoidCallback? onTap;
+
+  const AppMenuItem({
+    super.key,
+    required this.icon,
+    required this.title,
+    this.subtitle,
+    this.trailing,
+    this.onTap,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = ShadTheme.of(context);
+    return GestureDetector(
+      onTap: onTap,
+      behavior: HitTestBehavior.opaque,
+      child: Container(
+        margin: const EdgeInsets.symmetric(horizontal: 24, vertical: 2),
+        padding: const EdgeInsets.symmetric(horizontal: 4, vertical: 14),
+        decoration: BoxDecoration(
+          color: theme.colorScheme.card,
+          borderRadius: BorderRadius.circular(AppTheme.rSm),
+        ),
+        child: Row(children: [
+          Container(
+            width: 38,
+            height: 38,
+            decoration: BoxDecoration(
+              color: AppTheme.primaryLight,
+              borderRadius: BorderRadius.circular(AppTheme.rSm),
+            ),
+            child: Icon(icon, size: 22, color: AppTheme.primary),
+          ),
+          const SizedBox(width: AppTheme.sLg),
+          Expanded(
+            child: Column(
+              crossAxisAlignment: CrossAxisAlignment.start,
+              children: [
+                Text(title, style: TextStyle(fontSize: 19, fontWeight: FontWeight.w500, color: theme.colorScheme.foreground)),
+                if (subtitle != null && subtitle!.isNotEmpty)
+                  Padding(
+                    padding: const EdgeInsets.only(top: 2),
+                    child: Text(subtitle!, style: TextStyle(fontSize: 16, color: theme.colorScheme.mutedForeground)),
+                  ),
+              ],
+            ),
+          ),
+          if (trailing != null && trailing!.isNotEmpty)
+            Text(trailing!, style: TextStyle(fontSize: 17, color: theme.colorScheme.mutedForeground)),
+          const SizedBox(width: 4),
+          Icon(LucideIcons.chevronRight, size: 21, color: theme.colorScheme.mutedForeground),
+        ]),
+      ),
+    );
+  }
+}