feat: 顶部工具栏新增叠加图片按钮

css/style.css

@@ -222,6 +222,50 @@ html, body {
     overflow: hidden;
 }
 
+/* 层叠图层 - 位于背景图之上、文字之下 */
+.overlay-layer {
+    position: absolute;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+    pointer-events: none;
+}
+
+.overlay-layer .overlay-image {
+    position: absolute;
+    pointer-events: auto;
+    cursor: move;
+    touch-action: none;
+}
+
+.overlay-layer .overlay-image.selected {
+    outline: 2px dashed rgba(74, 144, 226, 0.8);
+    outline-offset: 2px;
+}
+
+.overlay-layer .overlay-image .delete-btn {
+    position: absolute;
+    top: -10px;
+    right: -10px;
+    width: 20px;
+    height: 20px;
+    background: #e74c3c;
+    color: #fff;
+    border: none;
+    border-radius: 50%;
+    font-size: 12px;
+    line-height: 20px;
+    text-align: center;
+    cursor: pointer;
+    display: none;
+    z-index: 10;
+}
+
+.overlay-layer .overlay-image.selected .delete-btn {
+    display: block;
+}
+
 /* 输入框图层 - 与背景图层隔离 */
 .preview-input-layer {
     position: absolute;