feat(remote): 文件传输改用Electron IPC通道

- 主进程新增4个IPC handler处理远程文件操作
- 前端通过IPC调用而非浏览器fetch访问远程API
- Remote服务新增3003端口专门处理文件传输
- 上传使用文件路径方案，下载使用保存对话框方案

remote/src/core/App.js

@@ -145,6 +145,7 @@ class App {
       const serverConfig = config.getSection('server') || {};
       return new Server({
         port: serverConfig.port || 3000,
+        fileTransferPort: serverConfig.fileTransferPort || 3003,
         host: serverConfig.host || '0.0.0.0'
       });
     });

remote/src/server/Server.js

@@ -5,9 +5,11 @@ const path = require('path');
 class Server {
   constructor(config = {}) {
     this.port = config.port || 3000;
+    this.fileTransferPort = config.fileTransferPort || 3003;
     this.host = config.host || '0.0.0.0';
     this.app = express();
     this.server = http.createServer(this.app);
+    this.fileTransferServer = null;
   }
 
   use(...args) {
@@ -28,20 +30,33 @@ class Server {
   start() {
     return new Promise((resolve, reject) => {
       this.server.listen({ port: this.port, host: this.host }, () => {
-        resolve(this.getAddress());
+        console.log(`Server started on port ${this.port}`);
       });
       this.server.on('error', reject);
+
+      this.fileTransferServer = http.createServer(this.app);
+      this.fileTransferServer.listen({ port: this.fileTransferPort, host: this.host }, () => {
+        console.log(`File transfer server started on port ${this.fileTransferPort}`);
+      });
+
+      resolve(this.getAddress());
     });
   }
 
   stop() {
     return new Promise((resolve, reject) => {
-      this.server.close((err) => {
-        if (err) {
-          reject(err);
-        } else {
-          resolve();
-        }
+      const closeFileTransfer = this.fileTransferServer 
+        ? new Promise((res) => this.fileTransferServer.close(res))
+        : Promise.resolve();
+      
+      closeFileTransfer.then(() => {
+        this.server.close((err) => {
+          if (err) {
+            reject(err);
+          } else {
+            resolve();
+          }
+        });
       });
     });
   }