fix: 修复复制地址提示层级问题，改用 toast 提示

- 创建统一的 ToastUtils 工具类
- 使用 BotToast.showCustomText 确保显示在所有弹窗之上
- 更新三处复制地址的代码使用新的 toast 方案
- 添加阴影效果提升视觉层次
- 支持成功/错误/警告等多种提示类型

flutter_monisuo/lib/core/utils/toast_utils.dart

@@ -0,0 +1,95 @@
+import 'package:flutter/material.dart';
+import 'package:bot_toast/bot_toast.dart';
+
+/// Toast 工具类 - 提供统一的 toast 提示功能
+/// 
+/// 使用 bot_toast 实现，确保 toast 显示在所有弹窗之上
+class ToastUtils {
+  ToastUtils._();
+
+  /// 显示普通提示
+  static void show(String message, {Duration? duration}) {
+    BotToast.showCustomText(
+      toastBuilder: (_) => _buildToastWidget(message),
+      align: Alignment.center,
+      duration: duration ?? const Duration(seconds: 2),
+      onlyOne: true,
+      crossPage: true,
+    );
+  }
+
+  /// 显示成功提示
+  static void showSuccess(String message, {Duration? duration}) {
+    BotToast.showCustomText(
+      toastBuilder: (_) => _buildToastWidget(
+        message,
+        backgroundColor: Colors.green.shade700,
+      ),
+      align: Alignment.center,
+      duration: duration ?? const Duration(seconds: 2),
+      onlyOne: true,
+      crossPage: true,
+    );
+  }
+
+  /// 显示错误提示
+  static void showError(String message, {Duration? duration}) {
+    BotToast.showCustomText(
+      toastBuilder: (_) => _buildToastWidget(
+        message,
+        backgroundColor: Colors.red.shade700,
+      ),
+      align: Alignment.center,
+      duration: duration ?? const Duration(seconds: 3),
+      onlyOne: true,
+      crossPage: true,
+    );
+  }
+
+  /// 显示警告提示
+  static void showWarning(String message, {Duration? duration}) {
+    BotToast.showCustomText(
+      toastBuilder: (_) => _buildToastWidget(
+        message,
+        backgroundColor: Colors.orange.shade700,
+      ),
+      align: Alignment.center,
+      duration: duration ?? const Duration(seconds: 2),
+      onlyOne: true,
+      crossPage: true,
+    );
+  }
+
+  /// 构建 toast widget
+  static Widget _buildToastWidget(
+    String message, {
+    Color? backgroundColor,
+  }) {
+    return Container(
+      padding: const EdgeInsets.symmetric(
+        horizontal: 24,
+        vertical: 12,
+      ),
+      decoration: BoxDecoration(
+        color: backgroundColor ?? Colors.black87,
+        borderRadius: BorderRadius.circular(8),
+        boxShadow: [
+          BoxShadow(
+            color: Colors.black.withOpacity(0.2),
+            blurRadius: 8,
+            offset: const Offset(0, 2),
+          ),
+        ],
+      ),
+      child: Text(
+        message,
+        style: const TextStyle(
+          color: Colors.white,
+          fontSize: 14,
+          fontWeight: FontWeight.w500,
+        ),
+        textAlign: TextAlign.center,
+      ),
+    );
+  }
+}