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_tab_chip.dart

@@ -0,0 +1,39 @@
+import 'package:flutter/material.dart';
+import '../core/app_theme.dart';
+
+/// 统一样式的标签/筛选 Chip
+class AppTabChip extends StatelessWidget {
+  final String label;
+  final bool selected;
+  final VoidCallback onTap;
+
+  const AppTabChip({
+    super.key,
+    required this.label,
+    required this.selected,
+    required this.onTap,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return GestureDetector(
+      onTap: onTap,
+      child: Container(
+        margin: const EdgeInsets.only(right: AppTheme.sSm),
+        padding: const EdgeInsets.symmetric(horizontal: AppTheme.sLg, vertical: AppTheme.sSm),
+        decoration: BoxDecoration(
+          color: selected ? AppTheme.primary : AppTheme.primaryLight,
+          borderRadius: BorderRadius.circular(AppTheme.rPill),
+        ),
+        child: Text(
+          label,
+          style: TextStyle(
+            fontSize: 16,
+            fontWeight: FontWeight.w500,
+            color: selected ? Colors.white : AppTheme.primary,
+          ),
+        ),
+      ),
+    );
+  }
+}