feat(remote): 实现文件下载真实进度显示

- 下载改用流式读取，计算真实进度百分比
- 通过 IPC 事件实时推送进度到前端
- 支持 Content-Length 计算下载进度

src/types/electron.d.ts

@@ -14,6 +14,7 @@ export interface ElectronAPI {
   onRemoteClipboardSyncToRemote: (callback: () => void) => () => void
   onRemoteClipboardSyncFromRemote: (callback: () => void) => () => void
   onRemoteClipboardAutoSync: (callback: (text: string) => void) => () => void
+  onDownloadProgress: (callback: (data: { progress: number; id: string }) => void) => () => void
   clipboardReadText: () => Promise<{ success: boolean; text?: string; error?: string }>
   clipboardWriteText: (text: string) => Promise<{ success: boolean; error?: string }>
   remoteFetchDrives: (serverHost: string, port: number, password?: string) => Promise<{
@@ -30,7 +31,7 @@ export interface ElectronAPI {
     success: boolean
     error?: string
   }>
-  remoteDownloadFile: (serverHost: string, port: number, fileName: string, remotePath: string, localPath: string, password?: string) => Promise<{
+  remoteDownloadFile: (id: string, serverHost: string, port: number, fileName: string, remotePath: string, localPath: string, password?: string) => Promise<{
     success: boolean
     filePath?: string
     error?: string