新增: 文件操作增强与预览扩展

- 文件剪贴板复制剪切粘贴，重名自动副本
- SFTP下载到本机与外部文件拖入，目录递归
- 传输进度浮动面板，transfer-progress事件链
- Drawio预览，Excel工作线程，冻结看门狗
- cmd与bat自写batch语法高亮，psm1等映射补齐

frontend/src/components/FileSystem/composables/useFileClipboard.ts

@@ -0,0 +1,41 @@
+/**
+ * 文件剪贴板 Composable（应用内内存态单例）
+ * 复制/剪切 → 粘贴到其他目录；粘贴动作由 index.vue 执行
+ */
+
+import { ref, computed } from 'vue'
+import type { FileItem } from '@/types/file-system'
+
+export type ClipboardMode = 'copy' | 'cut'
+
+interface FileClipboardState {
+  mode: ClipboardMode
+  items: FileItem[]
+  fromDir: string
+}
+
+// 模块级单例状态（跨组件共享）
+const state = ref<FileClipboardState | null>(null)
+
+export function useFileClipboard() {
+  const clipboard = computed(() => state.value)
+
+  const clipboardEmpty = computed(() => !state.value || state.value.items.length === 0)
+
+  /** 设置复制项 */
+  const setCopy = (items: FileItem[], fromDir: string) => {
+    state.value = { mode: 'copy', items: [...items], fromDir }
+  }
+
+  /** 设置剪切项 */
+  const setCut = (items: FileItem[], fromDir: string) => {
+    state.value = { mode: 'cut', items: [...items], fromDir }
+  }
+
+  /** 清空剪贴板 */
+  const clear = () => {
+    state.value = null
+  }
+
+  return { clipboard, clipboardEmpty, setCopy, setCut, clear }
+}