feat(图层管理): 添加图层管理面板及功能

- 新增图层面板UI组件，支持显示/隐藏图层
- 实现图层列表动态更新和选择功能
- 为所有图层元素添加唯一标识和隐藏状态控制
- 移除原有删除按钮，改为通过图层管理
- 在保存/恢复状态时处理图层可见性
- 优化预览生成逻辑，跳过隐藏图层

css/style.css

@@ -676,3 +676,223 @@ html, body {
 .grid-lines.visible {
     display: block;
 }
+
+/* ==================== 图层面板样式 ==================== */
+.layers-panel {
+    position: fixed;
+    top: 60px;
+    right: -280px;
+    width: 260px;
+    height: calc(100vh - 80px);
+    background: #fff;
+    border-left: 1px solid #e0e0e0;
+    box-shadow: -2px 0 10px rgba(0,0,0,0.1);
+    z-index: 200;
+    display: flex;
+    flex-direction: column;
+    transition: right 0.3s ease;
+}
+
+.layers-panel.active {
+    right: 0;
+}
+
+.layers-header {
+    display: flex;
+    justify-content: space-between;
+    align-items: center;
+    padding: 12px 16px;
+    border-bottom: 1px solid #e0e0e0;
+    background: #f8f8f8;
+}
+
+.layers-title {
+    font-size: 14px;
+    font-weight: 600;
+    color: #333;
+}
+
+.layers-close {
+    width: 24px;
+    height: 24px;
+    border: none;
+    background: transparent;
+    font-size: 18px;
+    color: #666;
+    cursor: pointer;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    border-radius: 4px;
+    transition: all 0.2s;
+}
+
+.layers-close:hover {
+    background: #e0e0e0;
+    color: #333;
+}
+
+.layers-list {
+    flex: 1;
+    overflow-y: auto;
+    padding: 8px;
+}
+
+.layer-item {
+    display: flex;
+    align-items: center;
+    padding: 10px 12px;
+    margin-bottom: 4px;
+    background: #f5f5f5;
+    border-radius: 6px;
+    cursor: pointer;
+    transition: all 0.2s;
+    border: 2px solid transparent;
+}
+
+.layer-item:hover {
+    background: #e8e8e8;
+}
+
+.layer-item.selected {
+    background: #e3f2fd;
+    border-color: #4a90e2;
+}
+
+.layer-item.hidden {
+    opacity: 0.5;
+    display: flex !important;
+}
+
+.layer-icon {
+    width: 24px;
+    height: 24px;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    margin-right: 10px;
+    font-size: 14px;
+}
+
+.layer-info {
+    flex: 1;
+    min-width: 0;
+}
+
+.layer-name {
+    font-size: 13px;
+    color: #333;
+    white-space: nowrap;
+    overflow: hidden;
+    text-overflow: ellipsis;
+}
+
+.layer-type {
+    font-size: 11px;
+    color: #999;
+    margin-top: 2px;
+}
+
+.layer-visibility {
+    width: 24px;
+    height: 24px;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    font-size: 14px;
+    font-weight: bold;
+    cursor: pointer;
+    padding: 4px;
+    border-radius: 4px;
+    transition: all 0.2s;
+    background: #4CAF50;
+    color: white;
+    border: 2px solid transparent;
+}
+
+.layer-visibility.is-hidden {
+    background: #f44336;
+    color: white;
+}
+
+.layer-visibility:hover {
+    opacity: 0.8;
+    transform: scale(1.1);
+}
+
+.layer-visibility:active {
+    transform: scale(0.95);
+}
+
+.layers-actions {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    gap: 4px;
+    padding: 12px;
+    border-top: 1px solid #e0e0e0;
+    background: #f8f8f8;
+    flex-wrap: wrap;
+}
+
+.layers-btn {
+    width: 32px;
+    height: 32px;
+    border: 1px solid #ddd;
+    background: #fff;
+    border-radius: 4px;
+    cursor: pointer;
+    font-size: 14px;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    transition: all 0.2s;
+}
+
+.layers-btn:hover {
+    background: #f0f0f0;
+    border-color: #ccc;
+}
+
+.layers-btn:disabled {
+    opacity: 0.3;
+    cursor: not-allowed;
+}
+
+.layers-btn-danger:hover {
+    background: #ffebee;
+    border-color: #ef5350;
+}
+
+.layers-divider {
+    width: 1px;
+    height: 24px;
+    background: #ddd;
+    margin: 0 4px;
+}
+
+/* 图层隐藏状态（用于画布上的元素） */
+.layer-hidden {
+    visibility: hidden !important;
+    pointer-events: none !important;
+}
+
+/* 移动端适配 */
+@media (max-width: 768px) {
+    .layers-panel {
+        width: 240px;
+        right: -260px;
+        top: 50px;
+        height: calc(100vh - 50px);
+    }
+    
+    .layers-actions {
+        padding: 8px;
+    }
+    
+    .layers-btn {
+        width: 28px;
+        height: 28px;
+        font-size: 12px;
+    }
+}