feat(Materials): add new materials navigation and href functions

- Introduced href functions for accessing materials, including hrefMaterials, hrefMaterialSubject, and hrefMaterialDetail.
- Updated AppsScreen to include a new entry for materials, enhancing the app's educational resources section.
- Exported material types in index.ts to support the new materials functionality.

src/screens/apps/AppsScreen.tsx

@@ -37,6 +37,13 @@ const APP_ENTRIES: AppItem[] = [
     icon: 'calendar-week',
     href: hrefs.hrefSchedule(),
   },
+  {
+    id: 'materials',
+    title: '学习资料',
+    subtitle: '按学科分类的学习资源网盘',
+    icon: 'folder-multiple',
+    href: hrefs.hrefMaterials(),
+  },
 ];
 
 export const AppsScreen: React.FC = () => {