Please provide the code changes or file diffs you would like me to summarize.

backend/src/main/java/com/sshmanager/config/SecurityConfig.java

@@ -17,8 +17,6 @@ import org.springframework.web.cors.CorsConfigurationSource;
 import org.springframework.web.cors.UrlBasedCorsConfigurationSource;
 
 import java.util.Arrays;
-import java.util.HashSet;
-import java.util.Set;
 
 @Configuration
 @EnableWebSecurity

backend/src/main/java/com/sshmanager/config/SpaForwardConfig.java

@@ -2,6 +2,7 @@ package com.sshmanager.config;
 
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.io.Resource;
+import org.springframework.lang.NonNull;
 import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
 import org.springframework.web.servlet.resource.PathResourceResolver;
@@ -15,13 +16,13 @@ import java.io.IOException;
 public class SpaForwardConfig implements WebMvcConfigurer {
 
     @Override
-    public void addResourceHandlers(ResourceHandlerRegistry registry) {
+    public void addResourceHandlers(@NonNull ResourceHandlerRegistry registry) {
         registry.addResourceHandler("/**")
                 .addResourceLocations("classpath:/static/")
                 .resourceChain(true)
                 .addResolver(new PathResourceResolver() {
                     @Override
-                    protected Resource getResource(String path, Resource location) throws IOException {
+                    protected Resource getResource(@NonNull String path, @NonNull Resource location) throws IOException {
                         Resource resource = location.createRelative(path);
                         if (resource.exists() && resource.isReadable()) {
                             return resource;

backend/src/main/java/com/sshmanager/config/TerminalHandshakeInterceptor.java

@@ -9,6 +9,8 @@ import org.springframework.web.socket.WebSocketHandler;
 import org.springframework.web.socket.server.HandshakeInterceptor;
 
 import javax.servlet.http.HttpServletRequest;
+import org.springframework.lang.NonNull;
+import org.springframework.lang.Nullable;
 import java.util.Map;
 
 @Component
@@ -21,8 +23,8 @@ public class TerminalHandshakeInterceptor implements HandshakeInterceptor {
     }
 
     @Override
-    public boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response,
+    public boolean beforeHandshake(@NonNull ServerHttpRequest request, @NonNull ServerHttpResponse response,
-                                  WebSocketHandler wsHandler, Map<String, Object> attributes) throws Exception {
+                                  @NonNull WebSocketHandler wsHandler, @NonNull Map<String, Object> attributes) throws Exception {
         if (!(request instanceof ServletServerHttpRequest)) {
             return false;
         }
@@ -50,7 +52,7 @@ public class TerminalHandshakeInterceptor implements HandshakeInterceptor {
     }
 
     @Override
-    public void afterHandshake(ServerHttpRequest request, ServerHttpResponse response,
+    public void afterHandshake(@NonNull ServerHttpRequest request, @NonNull ServerHttpResponse response,
-                              WebSocketHandler wsHandler, Exception exception) {
+                              @NonNull WebSocketHandler wsHandler, @Nullable Exception exception) {
     }
 }

backend/src/main/java/com/sshmanager/config/WebSocketConfig.java

@@ -5,6 +5,7 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.web.socket.config.annotation.EnableWebSocket;
 import org.springframework.web.socket.config.annotation.WebSocketConfigurer;
 import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry;
+import org.springframework.lang.NonNull;
 
 @Configuration
 @EnableWebSocket
@@ -20,7 +21,8 @@ public class WebSocketConfig implements WebSocketConfigurer {
     }
 
     @Override
-    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
+    @SuppressWarnings("null")
+    public void registerWebSocketHandlers(@NonNull WebSocketHandlerRegistry registry) {
         registry.addHandler(terminalWebSocketHandler, "/ws/terminal")
             .addInterceptors(terminalHandshakeInterceptor)
             // Docker/remote deployments often use non-localhost origins.

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

@@ -14,7 +14,6 @@ import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.security.core.Authentication;
-import org.springframework.stereotype.Component;
 import org.springframework.web.bind.annotation.*;
 import org.springframework.web.multipart.MultipartFile;
 import org.springframework.web.servlet.mvc.method.annotation.StreamingResponseBody;
@@ -33,7 +32,6 @@ import java.util.concurrent.Future;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.function.Supplier;
 import java.util.stream.Collectors;
-import java.util.stream.Stream;
 
 @RestController
 @RequestMapping("/api/sftp")
@@ -282,7 +280,7 @@ public class SftpController {
 
             return ResponseEntity.ok()
                 .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + filename + "\"")
-                .contentType(MediaType.APPLICATION_OCTET_STREAM)
+                .header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_OCTET_STREAM_VALUE)
                 .body(stream);
         } catch (Exception e) {
             return ResponseEntity.status(500).build();
@@ -331,12 +329,11 @@ public class SftpController {
             file.transferTo(tempFile);
             final java.io.File savedFile = tempFile;
             
-            UploadTaskStatus status = new UploadTaskStatus(taskId, userId, connectionId, 
+            UploadTaskStatus status = new UploadTaskStatus(taskId, userId, filename, file.getSize());
-                path, filename, file.getSize());
             status.setController(this);
             uploadTasks.put(taskKey, status);
             
-            Future<?> future = transferTaskExecutor.submit(() -> {
+            transferTaskExecutor.submit(() -> {
                 status.setStatus("running");
                 try {
                     withSessionLock(key, () -> {
@@ -387,8 +384,6 @@ public class SftpController {
                     }
                 }
             });
-            status.setFuture(future);
-            
             Map<String, Object> result = new HashMap<>();
             result.put("taskId", taskId);
             result.put("message", "Upload started");
@@ -654,6 +649,7 @@ public class SftpController {
     }
 
     @GetMapping("/transfer-remote/tasks/{taskId}/progress")
+    @SuppressWarnings("null")
     public SseEmitter streamTransferProgress(
             @PathVariable String taskId,
             Authentication authentication) {
@@ -692,6 +688,7 @@ public class SftpController {
     }
 
     @GetMapping("/upload/tasks/{taskId}/progress")
+    @SuppressWarnings("null")
     public SseEmitter streamUploadProgress(
             @PathVariable String taskId,
             Authentication authentication) {
@@ -739,6 +736,7 @@ public class SftpController {
         }
     }
     
+    @SuppressWarnings("null")
     private void broadcastProgress(String taskKey, Map<String, Object> data) {
         CopyOnWriteArrayList<SseEmitter> emitters = taskEmitters.get(taskKey);
         if (emitters == null || emitters.isEmpty()) {
@@ -976,10 +974,7 @@ public class SftpController {
     public static class UploadTaskStatus {
         private final String taskId;
         private final Long userId;
-        private final Long connectionId;
-        private final String path;
         private final String filename;
-        private final long fileSize;
         private final long createdAt;
         private volatile String status;
         private volatile String error;
@@ -987,17 +982,12 @@ public class SftpController {
         private volatile long finishedAt;
         private final AtomicLong totalBytes;
         private final AtomicLong transferredBytes;
-        private volatile Future<?> future;
         private volatile SftpController controller;
 
-        public UploadTaskStatus(String taskId, Long userId, Long connectionId, 
+        public UploadTaskStatus(String taskId, Long userId, String filename, long fileSize) {
-                                String path, String filename, long fileSize) {
             this.taskId = taskId;
             this.userId = userId;
-            this.connectionId = connectionId;
-            this.path = path;
             this.filename = filename;
-            this.fileSize = fileSize;
             this.createdAt = System.currentTimeMillis();
             this.status = "queued";
             this.totalBytes = new AtomicLong(fileSize);
@@ -1012,9 +1002,7 @@ public class SftpController {
             this.controller = controller;
         }
 
-        public void setFuture(Future<?> future) {
+        
-            this.future = future;
-        }
 
         public void setStatus(String status) {
             this.status = status;

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

@@ -12,6 +12,7 @@ import org.springframework.web.socket.CloseStatus;
 import org.springframework.web.socket.TextMessage;
 import org.springframework.web.socket.WebSocketSession;
 import org.springframework.web.socket.handler.TextWebSocketHandler;
+import org.springframework.lang.NonNull;
 
 import java.io.IOException;
 import java.io.InputStream;
@@ -46,7 +47,8 @@ public class TerminalWebSocketHandler extends TextWebSocketHandler {
     }
 
     @Override
-    public void afterConnectionEstablished(WebSocketSession webSocketSession) throws Exception {
+    @SuppressWarnings("null")
+    public void afterConnectionEstablished(@NonNull WebSocketSession webSocketSession) throws Exception {
         Long connectionId = (Long) webSocketSession.getAttributes().get("connectionId");
         String username = (String) webSocketSession.getAttributes().get("username");
 
@@ -101,7 +103,7 @@ public class TerminalWebSocketHandler extends TextWebSocketHandler {
     }
 
     @Override
-    protected void handleTextMessage(WebSocketSession webSocketSession, TextMessage message) throws Exception {
+    protected void handleTextMessage(@NonNull WebSocketSession webSocketSession, @NonNull TextMessage message) throws Exception {
         SshService.SshSession sshSession = sessions.get(webSocketSession.getId());
         if (sshSession != null && sshSession.isConnected()) {
             lastActivity.put(webSocketSession.getId(), System.currentTimeMillis());
@@ -122,7 +124,7 @@ public class TerminalWebSocketHandler extends TextWebSocketHandler {
     }
 
     @Override
-    public void afterConnectionClosed(WebSocketSession webSocketSession, CloseStatus status) throws Exception {
+    public void afterConnectionClosed(@NonNull WebSocketSession webSocketSession, @NonNull CloseStatus status) throws Exception {
         SshService.SshSession sshSession = sessions.remove(webSocketSession.getId());
         lastActivity.remove(webSocketSession.getId());
         if (sshSession != null) {

backend/src/main/java/com/sshmanager/entity/User.java

@@ -6,7 +6,6 @@ import lombok.AllArgsConstructor;
 
 import javax.persistence.*;
 import java.time.Instant;
-import java.time.temporal.ChronoUnit;
 
 @Data
 @NoArgsConstructor

backend/src/main/java/com/sshmanager/security/JwtAuthenticationFilter.java

@@ -8,6 +8,7 @@ import org.springframework.security.web.authentication.WebAuthenticationDetailsS
 import org.springframework.stereotype.Component;
 import org.springframework.util.StringUtils;
 import org.springframework.web.filter.OncePerRequestFilter;
+import org.springframework.lang.NonNull;
 
 import javax.servlet.FilterChain;
 import javax.servlet.ServletException;
@@ -27,8 +28,8 @@ public class JwtAuthenticationFilter extends OncePerRequestFilter {
     }
 
     @Override
-    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response,
+    protected void doFilterInternal(@NonNull HttpServletRequest request, @NonNull HttpServletResponse response,
-                                    FilterChain filterChain) throws ServletException, IOException {
+                                    @NonNull FilterChain filterChain) throws ServletException, IOException {
         try {
             String jwt = getJwtFromRequest(request);
             if (StringUtils.hasText(jwt) && tokenProvider.validateToken(jwt)) {

backend/src/main/java/com/sshmanager/security/PasswordExpirationFilter.java

@@ -7,6 +7,7 @@ import org.springframework.security.core.Authentication;
 import org.springframework.security.core.context.SecurityContextHolder;
 import org.springframework.stereotype.Component;
 import org.springframework.web.filter.OncePerRequestFilter;
+import org.springframework.lang.NonNull;
 
 import javax.servlet.FilterChain;
 import javax.servlet.ServletException;
@@ -29,7 +30,7 @@ public class PasswordExpirationFilter extends OncePerRequestFilter {
     }
 
     @Override
-    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
+    protected void doFilterInternal(@NonNull HttpServletRequest request, @NonNull HttpServletResponse response, @NonNull FilterChain filterChain)
             throws ServletException, IOException {
         Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
         if (authentication != null && authentication.isAuthenticated()) {

backend/src/main/java/com/sshmanager/service/BackupService.java

@@ -59,6 +59,7 @@ public class BackupService {
     }
 
     @Transactional
+    @SuppressWarnings("null")
     public BackupImportResponseDto importBackup(Long userId, BackupPackageDto backupPackage) {
         if (backupPackage == null) {
             throw new IllegalArgumentException("Backup package is required");

backend/src/main/java/com/sshmanager/service/ConnectionService.java

@@ -15,6 +15,7 @@ import java.util.List;
 import java.util.stream.Collectors;
 
 @Service
+@SuppressWarnings("null")
 public class ConnectionService {
 
     private final ConnectionRepository connectionRepository;

backend/src/test/java/com/sshmanager/controller/ConnectionControllerTest.java

@@ -28,17 +28,13 @@ import java.util.Optional;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
-import static org.mockito.ArgumentMatchers.any;
-import static org.mockito.ArgumentMatchers.anyLong;
-import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.doThrow;
 import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.verify;
-import static org.mockito.Mockito.verifyNoInteractions;
 import static org.mockito.Mockito.when;
 
 @ExtendWith(MockitoExtension.class)
+@SuppressWarnings("null")
 class ConnectionControllerTest {
 
     @Mock

backend/src/test/java/com/sshmanager/controller/SftpControllerTest.java

@@ -45,6 +45,7 @@ import static org.mockito.Mockito.verifyNoInteractions;
 import static org.mockito.Mockito.when;
 
 @ExtendWith(MockitoExtension.class)
+@SuppressWarnings("null")
 class SftpControllerTest {
 
     @Mock

backend/src/test/java/com/sshmanager/service/BackupServiceTest.java

@@ -26,6 +26,7 @@ import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 @ExtendWith(MockitoExtension.class)
+@SuppressWarnings("null")
 class BackupServiceTest {
 
     @Mock

backend/src/test/java/com/sshmanager/service/ConnectionServiceTest.java

@@ -27,6 +27,7 @@ import static org.mockito.Mockito.when;
 import static org.mockito.Mockito.lenient;
 
 @ExtendWith(MockitoExtension.class)
+@SuppressWarnings("null")
 class ConnectionServiceTest {
 
     @Mock

backend/src/test/java/com/sshmanager/service/SessionTreeLayoutServiceTest.java

@@ -23,6 +23,7 @@ import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 @ExtendWith(MockitoExtension.class)
+@SuppressWarnings("null")
 class SessionTreeLayoutServiceTest {
 
     @Mock

frontend/src/components/TransferCenterModal.tsx

@@ -115,7 +115,7 @@ export default function TransferCenterModal({
                   ...item,
                   progress: task.progress,
                   status: task.status,
-                  message: task.error || (task.status === 'success' ? '上传完成' : task.status === 'error' ? '上传失败' : task.status === 'cancelled' ? '已取消' : '正在传输...'),
+                  message: task.error || (task.status === 'success' ? '上传完成' : task.status === 'error' ? '上传失败' : '正在传输...'),
                 }
               : item,
           )
@@ -231,9 +231,9 @@ export default function TransferCenterModal({
                     <div className="rounded-xl border border-slate-700 bg-black px-4 py-3 text-sm text-slate-400">按浏览器任务并行执行</div>
                   </div>
                 </div>
-                <div className="flex-1 space-y-2">
+                <div className="flex min-h-0 flex-1 flex-col space-y-2">
-                  <span className="text-sm text-slate-300">3. 目标服务器</span>
+                  <span className="shrink-0 text-sm text-slate-300">3. 目标服务器</span>
-                  <div className="rounded-2xl border border-slate-700 bg-black p-2">
+                  <div className="min-h-0 flex-1 overflow-y-auto rounded-2xl border border-slate-700 bg-black p-2">
                     {connections.map((server) => {
                       const st = connectionStatuses[server.id]
                       const isOnline = st === 'online'