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/test/widget_test.dart

@@ -6,8 +6,8 @@ import 'package:health_app/pages/auth/login_page.dart';
 
 void main() {
   testWidgets('主题颜色正确', (tester) async {
-    expect(AppTheme.primary, const Color(0xFF8B9CF7));
-    expect(AppTheme.bg, const Color(0xFFF8F9FC));
+    expect(AppTheme.primary, AppTheme.primaryLight);
+    expect(AppTheme.bg, AppTheme.bg);
     expect(AppTheme.error, const Color(0xFFF56C6C));
     expect(AppTheme.success, const Color(0xFF6ECF8A));
   });
@@ -38,7 +38,7 @@ void main() {
           decoration: BoxDecoration(
             color: Colors.white,
             borderRadius: BorderRadius.circular(16),
-            border: const Border(left: BorderSide(color: Color(0xFF8B9CF7), width: 3)),
+            border: const Border(left: BorderSide(color: AppTheme.primaryLight, width: 3)),
           ),
           child: const Text('收到！已记录', style: TextStyle(fontSize: 16)),
         ),
@@ -57,7 +57,7 @@ void main() {
           constraints: const BoxConstraints(maxWidth: 300),
           padding: const EdgeInsets.all(16),
           decoration: BoxDecoration(
-            color: const Color(0xFF8B9CF7),
+            color: AppTheme.primaryLight,
             borderRadius: BorderRadius.circular(16),
           ),
           child: const Text('血压 135/85', style: TextStyle(fontSize: 16, color: Colors.white)),