init: 初始化 AssetX 项目仓库

包含 webapp（Next.js 用户端）、webapp-back（Go 后端）、
antdesign（管理后台）、landingpage（营销落地页）、
数据库 SQL 和配置文件。

webapp/components/common/Toast.tsx

@@ -0,0 +1,61 @@
+"use client";
+
+import { useEffect } from "react";
+
+type ToastType = "success" | "error" | "info" | "warning";
+
+interface ToastProps {
+  message: string;
+  type: ToastType;
+  isOpen: boolean;
+  onClose: () => void;
+  duration?: number;
+}
+
+export default function Toast({
+  message,
+  type,
+  isOpen,
+  onClose,
+  duration = 3000,
+}: ToastProps) {
+  useEffect(() => {
+    if (isOpen && duration > 0) {
+      const timer = setTimeout(() => {
+        onClose();
+      }, duration);
+      return () => clearTimeout(timer);
+    }
+  }, [isOpen, duration, onClose]);
+
+  if (!isOpen) return null;
+
+  const colors = {
+    success: "bg-green-50 dark:bg-green-900/20 border-green-200 dark:border-green-700 text-green-800 dark:text-green-200",
+    error: "bg-red-50 dark:bg-red-900/20 border-red-200 dark:border-red-700 text-red-800 dark:text-red-200",
+    info: "bg-blue-50 dark:bg-blue-900/20 border-blue-200 dark:border-blue-700 text-blue-800 dark:text-blue-200",
+    warning: "bg-yellow-50 dark:bg-yellow-900/20 border-yellow-200 dark:border-yellow-700 text-yellow-800 dark:text-yellow-200",
+  };
+
+  const icons = {
+    success: "✓",
+    error: "✕",
+    info: "ℹ",
+    warning: "⚠",
+  };
+
+  return (
+    <div className="fixed top-4 right-4 z-50 animate-in slide-in-from-top-2 fade-in duration-300">
+      <div className={`${colors[type]} border rounded-xl px-4 py-3 shadow-lg flex items-center gap-3 min-w-[300px] max-w-[400px]`}>
+        <span className="text-lg">{icons[type]}</span>
+        <span className="text-sm font-medium flex-1">{message}</span>
+        <button
+          onClick={onClose}
+          className="text-current opacity-50 hover:opacity-100 transition-opacity"
+        >
+          ✕
+        </button>
+      </div>
+    </div>
+  );
+}