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/widgets/app_future_view.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 import '../core/app_colors.dart';
 import 'app_error_state.dart';
 
@@ -49,3 +50,35 @@ class AppFutureView<T> extends StatelessWidget {
     );
   }
 }
+
+/// Riverpod 异步数据视图。Provider 会保留最近一次成功数据，刷新时不清空页面。
+class AppAsyncValueView<T> extends StatelessWidget {
+  final AsyncValue<T> value;
+  final Widget Function(BuildContext context, T data) onData;
+  final VoidCallback? onRetry;
+  final Widget? loading;
+  final String? errorTitle;
+
+  const AppAsyncValueView({
+    super.key,
+    required this.value,
+    required this.onData,
+    this.onRetry,
+    this.loading,
+    this.errorTitle,
+  });
+
+  @override
+  Widget build(BuildContext context) => value.when(
+    skipLoadingOnRefresh: true,
+    skipLoadingOnReload: true,
+    data: (data) => onData(context, data),
+    error: (_, _) =>
+        AppErrorState(title: errorTitle ?? '加载失败', onRetry: onRetry),
+    loading: () =>
+        loading ??
+        const Center(
+          child: CircularProgressIndicator(color: AppColors.primary),
+        ),
+  );
+}