refactor(ui): 简化卡片组件视觉样式并扩展引导流程

统一移除 InfoCard 和药品详情页面的阴影与边框装饰，实现更简洁的界面风格
新增用药管理引导页面，完善用户首次使用体验
添加药品管理相关插图资源，增强视觉引导效果

app/medications/[medicationId].tsx

@@ -1149,14 +1149,7 @@ const styles = StyleSheet.create({
     justifyContent: 'space-between',
     backgroundColor: '#FFFFFF',
     alignItems: 'center',
-    shadowColor: '#7a5af8',
-    shadowOpacity: 0.12,
-    shadowRadius: 16,
-    shadowOffset: { width: 0, height: 4 },
-    elevation: 5,
     gap: 12,
-    borderWidth: 1,
-    borderColor: 'rgba(122, 90, 248, 0.08)',
   },
   heroInfo: {
     flexDirection: 'row',
@@ -1208,13 +1201,6 @@ const styles = StyleSheet.create({
     flexDirection: 'row',
     alignItems: 'center',
     justifyContent: 'space-between',
-    shadowColor: '#000',
-    shadowOpacity: 0.06,
-    shadowRadius: 12,
-    shadowOffset: { width: 0, height: 3 },
-    elevation: 3,
-    borderWidth: 1,
-    borderColor: 'rgba(0, 0, 0, 0.04)',
   },
   fullCardLeading: {
     flexDirection: 'row',
@@ -1240,14 +1226,7 @@ const styles = StyleSheet.create({
     gap: 14,
     borderRadius: 24,
     paddingHorizontal: 18,
-    paddingVertical: 16,
-    shadowColor: '#000',
-    shadowOpacity: 0.06,
-    shadowRadius: 12,
-    shadowOffset: { width: 0, height: 3 },
-    elevation: 3,
-    borderWidth: 1,
-    borderColor: 'rgba(0, 0, 0, 0.04)',
+    paddingVertical: 16
   },
   noteBody: {
     flex: 1,

app/onboarding.tsx

@@ -47,6 +47,12 @@ const SLIDES: OnboardingSlide[] = [
     description: '个性化断食方案，智能提醒与进度追踪，助你改善代谢，科学控脂。',
     image: require('@/assets/images/onboarding/fasting.jpg'),
   },
+  {
+    key: 'medication',
+    title: '智能用药管理',
+    description: '个性化用药提醒，智能追踪服药记录，确保按时按量，守护您的健康安全。',
+    image: require('@/assets/images/onboarding/medicine.jpg'),
+  },
   {
     key: 'support',
     title: '健康挑战赛',

components/ui/InfoCard.tsx

@@ -87,14 +87,7 @@ const styles = StyleSheet.create({
     padding: 16,
     backgroundColor: '#FFFFFF',
     gap: 6,
-    shadowColor: '#000',
-    shadowOpacity: 0.06,
-    shadowRadius: 12,
-    shadowOffset: { width: 0, height: 3 },
-    elevation: 3,
     position: 'relative',
-    borderWidth: 1,
-    borderColor: 'rgba(0, 0, 0, 0.04)',
   },
   infoCardArrow: {
     position: 'absolute',