ux: Toast 提示替代 alert，自动消失无需手动点击

web/static/style.css

@@ -453,6 +453,37 @@ button {
     justify-content: center;
 }
 
+/* Toast 提示 */
+.toast {
+    position: fixed;
+    top: 80px;
+    left: 50%;
+    transform: translateX(-50%);
+    background: #333;
+    color: white;
+    padding: 12px 24px;
+    border-radius: 8px;
+    z-index: 2000;
+    font-size: 14px;
+    box-shadow: 0 4px 12px rgba(0,0,0,0.3);
+    animation: fadeIn 0.3s;
+}
+
+.toast.fade-out {
+    animation: fadeOut 0.3s;
+    opacity: 0;
+}
+
+@keyframes fadeIn {
+    from { opacity: 0; transform: translateX(-50%) translateY(-10px); }
+    to { opacity: 1; transform: translateX(-50%) translateY(0); }
+}
+
+@keyframes fadeOut {
+    from { opacity: 1; }
+    to { opacity: 0; }
+}
+
 /* 响应式 */
 @media (max-width: 768px) {
     .control-panel {