feat: 三端抽屉重构 + 配色系统更新 + 后台管理页精调 + 键盘抬起组件

## 抽屉重构
- admin_drawer / doctor_drawer / health_drawer 三端抽屉全部重做
- drawer_shell 增强

## 配色系统
- app_colors / app_module_visuals / app_theme 更新
- app.dart 启动流程调整

## 后台管理页
- admin_doctors_page 大幅重构(+251)
- admin_home / doctor_dashboard / doctor_reports / doctor_home / doctor_followups / doctor_settings 精调

## 患者端
- home_page / chat_messages_view / medication_list / notification_center / remaining_pages / exercise_plan / device / diet / consultation 微调

## 新增
- keyboard_lift.dart: 键盘抬起处理组件
- AGENTS.md: agent 指引文档

## 其他
- api_client IP 适配
- app_future_view 增强
- data_providers 调整
- secondary_page_visuals_test 更新

health_app/lib/pages/admin/admin_home_page.dart

@@ -16,31 +16,48 @@ class AdminPageNotifier extends Notifier<String> {
   void set(String page) => state = page;
 }
 
-class AdminHomePage extends ConsumerWidget {
+class AdminHomePage extends ConsumerStatefulWidget {
   const AdminHomePage({super.key});
 
   @override
-  Widget build(BuildContext context, WidgetRef ref) {
-    final page = ref.watch(adminPageProvider);
+  ConsumerState<AdminHomePage> createState() => _AdminHomePageState();
+}
 
-    return Scaffold(
-      backgroundColor: AppColors.pageGrey,
-      appBar: AppBar(
-        backgroundColor: Colors.transparent,
-        elevation: 0,
-        title: Text(
-          page == 'patients' ? '患者管理' : '医生管理',
-          style: TextStyle(color: AppColors.textPrimary),
+class _AdminHomePageState extends ConsumerState<AdminHomePage> {
+  final List<Widget?> _pages = [const AdminDoctorsPage(), null];
+
+  @override
+  Widget build(BuildContext context) {
+    final page = ref.watch(adminPageProvider);
+    final pageIndex = page == 'patients' ? 1 : 0;
+    _pages[pageIndex] ??= const AdminPatientsPage();
+
+    return PopScope(
+      canPop: page == 'doctors',
+      onPopInvokedWithResult: (didPop, _) {
+        if (!didPop) ref.read(adminPageProvider.notifier).set('doctors');
+      },
+      child: Scaffold(
+        backgroundColor: AppColors.pageGrey,
+        drawerEnableOpenDragGesture: true,
+        appBar: AppBar(
+          backgroundColor: Colors.transparent,
+          elevation: 0,
+          title: Text(
+            page == 'patients' ? '患者管理' : '医生管理',
+            style: TextStyle(color: AppColors.textPrimary),
+          ),
+          iconTheme: const IconThemeData(color: AppColors.textPrimary),
+        ),
+        drawer: const AdminDrawer(),
+        body: BackofficeSurface(
+          child: IndexedStack(
+            index: pageIndex,
+            children: _pages
+                .map((page) => page ?? const SizedBox.shrink())
+                .toList(growable: false),
+          ),
         ),
-        iconTheme: const IconThemeData(color: AppColors.textPrimary),
-      ),
-      drawer: const AdminDrawer(),
-      body: BackofficeSurface(
-        child: switch (page) {
-          'doctors' => const AdminDoctorsPage(),
-          'patients' => const AdminPatientsPage(),
-          _ => const AdminDoctorsPage(),
-        },
       ),
     );
   }