Fix: 修复 Docker 上传目录解析错误

将 multipart 上传目录改为基于 DATA_DIR 的绝对路径，避免 Tomcat 在容器内把相对路径解析到临时目录。同步让上传控制器复用该配置并补充错误日志，确保本地文件在异步上传期间可用。

backend/src/main/java/com/sshmanager/controller/SftpController.java

@@ -9,6 +9,7 @@ import com.sshmanager.service.ConnectionService;
 import com.sshmanager.service.SftpService;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
@@ -43,6 +44,7 @@ public class SftpController {
     private final ConnectionService connectionService;
     private final UserRepository userRepository;
     private final SftpService sftpService;
+    private final String uploadTempLocation;
 
     private final Map<String, SftpService.SftpSession> sessions = new ConcurrentHashMap<>();
     private final Map<String, Object> sessionLocks = new ConcurrentHashMap<>();
@@ -53,10 +55,12 @@ public class SftpController {
 
     public SftpController(ConnectionService connectionService,
                           UserRepository userRepository,
-                          SftpService sftpService) {
+                          SftpService sftpService,
+                          @Value("${spring.servlet.multipart.location:/app/data/upload-temp}") String uploadTempLocation) {
         this.connectionService = connectionService;
         this.userRepository = userRepository;
         this.sftpService = sftpService;
+        this.uploadTempLocation = uploadTempLocation;
     }
 
     private Long getCurrentUserId(Authentication auth) {
@@ -297,9 +301,9 @@ public class SftpController {
             String taskKey = uploadTaskKey(userId, taskId);
             
             // Save file to persistent location before async processing
-            java.io.File uploadTempDir = new java.io.File("./data/upload-temp");
-            if (!uploadTempDir.exists()) {
-                uploadTempDir.mkdirs();
+            java.io.File uploadTempDir = new java.io.File(uploadTempLocation);
+            if (!uploadTempDir.exists() && !uploadTempDir.mkdirs()) {
+                throw new IOException("Failed to create upload temp directory: " + uploadTempDir.getAbsolutePath());
             }
             tempFile = new java.io.File(uploadTempDir, taskId + "_" + file.getOriginalFilename());
             file.transferTo(tempFile);
@@ -352,6 +356,8 @@ public class SftpController {
                         }
                     });
                 } catch (Exception e) {
+                    log.error("Async upload failed, taskId={}, connectionId={}, tempFile={}",
+                            taskId, connectionId, savedFile.getAbsolutePath(), e);
                     status.markError(e.getMessage() != null ? e.getMessage() : "Upload failed");
                     // Clean up temp file on error
                     if (savedFile.exists()) {
@@ -366,6 +372,7 @@ public class SftpController {
             result.put("message", "Upload started");
             return ResponseEntity.ok(result);
         } catch (Exception e) {
+            log.error("Failed to prepare upload temp file, connectionId={}", connectionId, e);
             // Clean up temp file if initial save failed
             if (tempFile != null && tempFile.exists()) {
                 tempFile.delete();

backend/src/main/resources/application.yml

@@ -9,7 +9,7 @@ spring:
     multipart:
       max-file-size: 2048MB
       max-request-size: 2048MB
-      location: ./data/upload-temp  # 持久化临时目录，避免 Docker 容器重启丢失
+      location: ${DATA_DIR:/app/data}/upload-temp  # 使用容器数据目录，避免被解析为 Tomcat 工作目录
       file-size-threshold: 0  # 立即写入磁盘，不使用内存缓冲
   datasource:
     url: jdbc:h2:file:./data/sshmanager;DB_CLOSE_DELAY=-1